How to fix "Incorrect function" error in Windows?

"Incorrect function" is the text of Windows system error 1 (ERROR_INVALID_FUNCTION): a program asked Windows, a drive or a driver for something it cannot do. The fix depends on where you see it. A pop-up at sign-in that names Win32Bridge.Server.exe is the most common case, and resetting Cortana usually ends it.

Facts checked on 15 October 2026. Steps written for Windows 11 (25H2 and 26H2) and Windows 10 22H2.

What the "Incorrect function" error means

"Incorrect function." is not a message that one program writes. It is the text Windows gives for system error code 1. Microsoft's list of system error codes reads: ERROR_INVALID_FUNCTION, 1 (0x1), Incorrect function. Any program that gets this code back from Windows and shows it to you prints the same two words. That is why people see it at sign-in, during setup, in File Explorer and in DISM.

Code

1 (hex 0x1), ERROR_INVALID_FUNCTION

Text

"Incorrect function." (with a full stop). DISM shows it as "Error: 1" followed by the same text.

In plain words

The program asked Windows, a drive or a driver to do something that this target does not support or cannot do right now.

What names the cause

The path, program or drive letter in the same window, never the two words alone.

The most common window looks like this. Its title and first line show the path of the program that failed, and the last line is the error. The version number in the path differs from PC to PC:

C:\Program Files\WindowsApps\Microsoft.549981C3F5F10_3.2106.14307.0_x64__8wekyb3d8bbwe\Win32Bridge.Server.exe
Incorrect function.

Microsoft.549981C3F5F10 is the package name of the Cortana app, so this pop-up is Cortana failing to start, not a virus and not a problem with your files. People who search "incorrect function error", "windows incorrect function" or the misspelled "incorect function" usually have this window.

Why you get "Incorrect function", most likely first

• Most often: the Win32Bridge.Server.exe pop-up. It is the case the reader above has, and the one most search queries describe ("incorrect function when logging in windows 11").
• Often: setup.exe on a virtual drive. Queries such as "setup.exe incorrect function" and "d setup exe incorrect function" point to an installer started from a mounted image.
• Sometimes: a drive that will not open, usually a newly installed, moved or external disk.
• Rarely: BitLocker and DISM. These show the code in a command window, and the program's own log says more.

How to fix the "Incorrect function" error

Pick the fix by the window you see. The sign-in pop-up needs Fix 1 or Fix 2 only. The other cases each have their own fix, and Fix 7 is the general repair when nothing else matches.

Fix 1. Repair or reset the Cortana app (Win32Bridge.Server.exe pop-up)

2 minutesNo riskThe "Incorrect function" pop-up appears at every start or sign-in and its path ends in Win32Bridge.Server.exe.

Win32Bridge.Server.exe lives inside the Cortana package (Microsoft.549981C3F5F10). Repair checks the app's files and Reset clears its data, which ends a broken start. On Microsoft Q&A, resetting Cortana is the accepted answer that over 100 users marked as helpful, and one reported that Repair alone was enough.

1. Press Win + I to open Settings.
2. On Windows 11, open Apps > Installed apps. On Windows 10, open Apps > Apps & features.
3. Find Cortana. On Windows 11, select the three dots next to it and then Advanced options. On Windows 10, select Cortana and then Advanced options.
4. Select Terminate to stop the app.
5. Select Repair and restart the PC. If the pop-up does not appear, you are done.
6. If it appears again, go back to the same page and select Reset, then restart.

Reset deletes the app's local data, which for Cortana means only its settings. The general steps for any app are here: How to repair or reset an app in Windows

Fix 2. Stop Cortana from starting, or remove it

5 minutesLow riskFix 1 did not help, the pop-up returns, or you never use Cortana.

Microsoft retired Cortana as a standalone Windows app in spring 2023 and points users to Copilot and voice access instead. The app no longer does anything useful, so keeping it from starting removes the only thing that runs Win32Bridge.Server.exe.

1. Press Ctrl + Shift + Esc to open Task Manager.
2. Open Startup apps in the left column on Windows 11, or the Startup tab on Windows 10.
3. Right-click Cortana and select Disable. Restart the PC.
4. If the pop-up still appears, remove the app. Right-click Start, select Terminal on Windows 11 or Windows PowerShell on Windows 10.
5. Remove Cortana for your account:

   Get-AppxPackage *Microsoft.549981C3F5F10* | Remove-AppxPackage

6. Restart the PC.

Startup apps in general: Stop apps from opening at startup. More about removing built-in apps with PowerShell, and how to get one back from the Microsoft Store: Remove built-in Windows apps with PowerShell

Fix 3. Fix setup.exe "Incorrect function" on a mounted ISO

5 minutesNo riskYou opened an ISO or BIN image with a third-party tool and running setup.exe from the new drive (often D: or E:) gives "Incorrect function".

The error comes from the virtual drive, not from the installer: the drive driver of the ISO tool does not support a request setup.exe makes. Users on Windows forums report it mostly with PowerISO and say it goes away with Windows' own Mount, which has been built into Windows 10 and Windows 11 for ISO files.

1. Open File Explorer > This PC, right-click the virtual drive and select Eject, or unmount it in the ISO tool.
2. Right-click the .iso file and select Mount. On Windows 11, it may be under Show more options.
3. Open the new drive in This PC and run setup.exe again.
4. If it still fails, copy all files from the mounted drive to a new folder such as C:\Setup and run setup.exe from there.
5. If the publisher lists a checksum for the ISO, compare it. Run this in Terminal, with your own file path:

   Get-FileHash "C:\Users\you\Downloads\file.iso" -Algorithm SHA256

6. If the hash differs, download the image again from the publisher.

Fix 4. Make Windows see the drive again: rescan disks and reinstall the driver

10 minutesLow riskFile Explorer says the drive is not accessible with "Incorrect function", usually right after you added, moved or connected a disk.

When Windows' picture of the disk is stale, or its driver did not load cleanly, every request to the drive fails with error 1. A rescan and a fresh driver make Windows read the disk again. Disk Management also shows whether the disk has a file system Windows can read at all.

1. Right-click Start and select Disk Management.
2. Select Action > Rescan Disks and wait until the list refreshes.
3. Look at the drive. If its partition shows RAW or no file system, Windows cannot read it: see the warning below.
4. Right-click Start, select Device Manager and expand Disk drives.
5. Right-click the drive, select Uninstall device and confirm. Restart the PC: Windows installs the driver again.
6. If the drive now opens but shows errors, check it: Check a disk for errors (chkdsk)

The full driver steps, including updating and rolling back: Update, roll back or reinstall a driver

Fix 5. Clear the read-only flag on the disk with DiskPart

5 minutesLow riskThe drive opens but copying or saving to it fails, or DiskPart reports it as read-only.

A disk marked read-only refuses every write, and some programs report that refusal as "Incorrect function". DiskPart shows the flag and clears it.

1. Right-click Start and select Terminal (Admin) on Windows 11 or Windows PowerShell (Admin) on Windows 10. Select Yes.
2. Type diskpart and press Enter.
3. Type list disk and press Enter. Find your drive by its size.
4. Type select disk 1, using your disk's number, not its drive letter, and press Enter.
5. Type attributes disk and press Enter. Look at Current Read-only State.
6. If it says Yes, type attributes disk clear readonly and press Enter.
7. Type exit and test the drive.

Fix 6. Turn off BitLocker when it fails with "Incorrect function"

15 minutes plus decryption timeRead the warningTurning off BitLocker in Control Panel or Settings stops with "Incorrect function".

Decryption needs the drive unlocked and not busy. Running manage-bde from Windows Recovery, where the system drive is not in use, lets the decryption start where it failed inside Windows.

1. Open Control Panel > System and Security > BitLocker Drive Encryption and select Back up your recovery key. Save or print it.
2. Try in Windows first. Open Terminal (Admin) and run:

   manage-bde -status C:
   manage-bde -off C:

3. If that fails with "Incorrect function", hold Shift and select Start > Power > Restart.
4. Select Troubleshoot > Advanced options > Command Prompt. Enter the recovery key if Windows asks.
5. Find the drive letter (it can differ from C: in Windows Recovery), open it with your key and start decryption:

   manage-bde -status
   manage-bde -unlock C: -RecoveryPassword 111111-222222-333333-444444-555555-666666-777777-888888
   manage-bde -off C:

6. Use your own key and drive letter. Run manage-bde -status from time to time and restart only when it shows Fully Decrypted.

Fix 7. Repair Windows system files (DISM "Error: 1" and other programs)

20 to 40 minutesLow riskDISM ends with "Error: 1 Incorrect function", or another Windows program shows the message and none of the cases above fits.

When a Windows component itself is damaged, its requests fail with error 1. SFC and DISM replace damaged system files; if DISM is the program that fails, its log names the step that went wrong.

1. Run DISM and SFC from an administrator window as shown here: Run DISM and SFC to repair Windows system files
2. If DISM ends with Error: 1, open C:\Windows\Logs\DISM\dism.log in Notepad and search for Error near the end. The line before it names the operation that failed.
3. Run DISM only from an administrator window inside Windows when you use /Online. In Windows Recovery, point it at the offline system with /Image:C:\ instead.
4. Restart and try the program that showed the error again.

If the error started after an update or a new program, a restore point from before that day is the quickest way back: Undo recent changes with System Restore

Still seeing "Incorrect function": where the real cause is written

• Event Viewer: press Win + R, type eventvwr.msc, open Windows Logs > Application and System, and look for errors at the time the message appeared. The source name tells you which program or driver failed.
• BitLocker: Applications and Services Logs > Microsoft > Windows > BitLocker-API > Management records why encryption or decryption stopped.
• DISM and SFC: C:\Windows\Logs\DISM\dism.log and C:\Windows\Logs\CBS\CBS.log.
• What to send to support: the full text of the window including the path, your Windows version from winver, the matching Event Viewer entry and the fixes you already tried.

How to keep "Incorrect function" from coming back

Frequently asked questions

What does "Incorrect function" mean in Windows?

It is the text of Windows system error code 1, ERROR_INVALID_FUNCTION, hex 0x1. A program asked Windows, a driver or a drive for an action that this target does not support or cannot do at that moment. The message is shared by many programs, so the two words alone do not tell you the cause. The path or program named in the same window does. Win32Bridge.Server.exe points to Cortana (Fix 1), setup.exe on a virtual drive points to the ISO tool (Fix 3).

What is Win32Bridge.Server.exe and is it safe?

Win32Bridge.Server.exe is a file inside the Cortana app package, Microsoft.549981C3F5F10, in C:\Program Files\WindowsApps. It is a Microsoft file, not malware, when it sits in that folder. The "Incorrect function" pop-up means Cortana failed when it tried to start with Windows. Repair or reset Cortana (Fix 1), or remove it (Fix 2). Microsoft retired Cortana as a standalone Windows app in spring 2023, so you lose nothing by removing it.

Why do I get "Incorrect function" when logging in to Windows 11?

Almost always because the Cortana app starts at sign-in and fails, and the pop-up names Win32Bridge.Server.exe. Windows 11 still carries the Cortana package on many PCs that were upgraded from Windows 10. Open Settings > Apps > Installed apps > Cortana > Advanced options and select Repair, then Reset if needed (Fix 1). If the pop-up returns, disable Cortana in Task Manager's Startup apps or remove it with PowerShell (Fix 2).

How do I fix setup.exe "Incorrect function" on Windows 11?

Eject the virtual drive that a third-party tool created, right-click the ISO file and select Mount, then run setup.exe from the new drive (Fix 3). Users report this error mostly with PowerISO virtual drives, and the built-in Mount avoids it. If it still fails, copy all files to a local folder such as C:\Setup and run setup.exe there. If that fails too, compare the ISO's SHA256 hash with the publisher's and download it again if they differ.

Why does PowerISO show "Incorrect function"?

Users on Windows forums report that setup.exe opened from a PowerISO virtual drive fails with "Incorrect function", while the same image works when mounted another way. The virtual drive driver does not answer a request the installer makes. Update PowerISO to its latest version, or eject its drive and use Windows' own Mount for ISO files. We could not find a statement from PowerISO's maker about this error, so treat it as a user report.

What is DISM "Error: 1 Incorrect function"?

It is the same error code 1, reported by DISM. The DISM log at C:\Windows\Logs\DISM\dism.log names the operation that failed: open it and search for Error near the end. Make sure you run DISM from an administrator window inside Windows when you use /Online, and use /Image:C:\ when you run it from Windows Recovery. We could not confirm one single cause from Microsoft, so the log is the place to look (Fix 7).

Why does a drive say "not accessible, Incorrect function"?

Windows cannot read the disk. Most often the disk is new or moved and Windows has a stale view of it, the driver did not load, the disk uses a file system Windows does not read, or the disk is failing. Rescan disks in Disk Management and reinstall the driver in Device Manager (Fix 4). If the partition shows RAW and holds files you need, do not format it. A disk that fails on a second PC is a hardware problem.

Can "Incorrect function" stop BitLocker from turning off?

Yes, some users get it when they turn off BitLocker. Back up the recovery key first, then try manage-bde -off C: from an administrator Terminal. If that fails, start Windows Recovery, open Command Prompt, open the drive with manage-bde -unlock and your recovery key, and run manage-bde -off there (Fix 6). Watch progress with manage-bde -status and keep the PC on power until it shows Fully Decrypted.

I saw "Incorrect function" when opening an image or a program. What now?

Look at the path in the error window. If it names a Store app, repair or reset that app in Settings > Apps > Installed apps > Advanced options, as in Fix 1. If it names a file on an external or network drive, test the drive with Fix 4. If it names a Windows program, run SFC and DISM (Fix 7). The error itself only says the request failed; the path tells you which part to repair.

I searched in another language. Is this the same error?

Yes. Searches such as "ارور incorrect function" and "رفع ارور incorrect function" (Persian for "incorrect function error" and "fix the incorrect function error"), "incorrect function แก้ยังไง" (Thai, "how to fix") and the Spanish Windows text "función incorrecta" all describe Windows error 1. The fixes on this page are the same on any Windows language; only the menu names are translated. Start with the window the message appears in and the chooser above.