Can't open Task Manager

When I right click on my task bar and click on Start Task Manager it gives me an error

Windows cannot find "C:\windows\system32\taskmgr.exe" Make sure you have typed the name correctly and try again.

So I tried executing task manager from system32 directory, still it gives me the same error.

Has my task manager gone corrupt ? If so how can I reinstall it?

Thanks.

Additional information for the case:

• running sfc /verifyonly resulted in Windows Resource Protection did not find any integrity violations.
• On Windows 7 Home Premium Engish 64bit: size of "C:\Windows\System32\taskmgr.exe" is 257 024 bytes, it's md5 is 09f7401d56f2393c6ca534ff0241a590, crc-32 is d5b3f6f7.
• Permissions of taskmgr.exe are: Read & execute + Read for SYSTEM, Administrators and Users, Full Control for TrustedInstaller
• virustotal.com says the file is virus-free
• in Windows Logs/Application I found a warning by winlogon saying The Windows logon process has failed to spawn a user application. Application name: taskmgr.exe. Command line parameters: taskmgr.exe /3 . that is apparently relavant to the problem,
• in Windows Logs/System I found an error by "VDS Basic Provider" saying Unexpected failure. Error code: 490@01010004 that is apparently relavant to the problem

1. Download sysinternals suite from microsoft technet and unpack.
2. Find and run procexp.exe.
3. Click in Options menu on Replace Task Manager and than Restore Task Manager.
4. Click Ctrl+Alt+Del or on taskbar Run Taskmanager. Settings are restored and MS Taskmanager works fine. Because of my habit I can´t work without sysinternals.

Process explorer by Sysinternals is one solution but there is another.

Use the built in System File Checker tool in Windows 7

Open a run command box or elevated command prompt and type in

sfc /scannow

it will now scan all your Windows system files and replace any that are missing or corrupt.

Source of Information

I had the same problem and I could not even fix it with process explorer. The culprit was the value "Debugger" under "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\taskmgr.exe". Some older installation of Process Explorer which had not been properly uninstalled had registered itself as the debugger of taskmgr.exe by storing its path in there, but that path did not exist anymore, so windows would refuse to run taskmgr.exe because it could not find the debugger for it. Deleting the "Debugger" value fixed the problem.