explorer.exe error on windows 7

Here's how to fix this issue:
1. CTRL-Alt-Del to bring up Task Manager.
2. Click File | New Task(run).
3. Type regedit in the Run box and click OK.
4. Browse to the following registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution.options
5. Under this key there will be subkeys named explorer.exe and iexplorer.exe. Delete the explorer and iexplorer keys entirely. They should not be listed under the Image File Execution.Options key.
6. Close the Registry Editor.
7. Restart the computer.
Assuming no other viruses / adware / spyware / malware are interfering, the Windows desktop should load fine now.

OR

hxxp://en.kioskea.net/forum/affich-9082-explorer-exe-corrupted-or-infected
Click Start.
In the Search Bar, type regedit and press Enter.
Locate the following key: HKEY_LOCAL_MACHINE\SOFTWARE\ Microsoft\ SQMClient\Windows\DisabledSessions
In the right pane delete this subkey: MachineThrottling
Turn your computer off and back on for the change to take effect.

OR

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Shell <- Check "explorer.exe"

OR

1. insert Windows 7 installer DVD
2. Browse DVD -> You find folder name "sources"
3.Then you will find "install.wim"
4. Extract with "7 Zip" software
5. under "Windows" Folder -> explorer.exe -> copy to c:\files
6. under "Windows\system32\" Folder -> shell32.dll -> copy to c:\files
7. On your machine, do the followings

c:\windows>takeown   /f      explorer.exe
c:\windows>icacls      explorer.exe            /grant          zawhtet:F
c:\windows>rename   explorer.exe             explorer.exe_old
c:\windows>move      explorer.exe_old      c:\files
c:\files>copy               explorer.exe             c:\windows\


c:\windows\system32> takeown    /f    shell32.dll
c:\windows\system32>icacls         shell32.dll           /grant         zawhtet:F
c:\windows\system32>rename       shell32.dll           shell32.dll_old
c:\windows\system32>move          shell32.dll             c:\files
c:\files>copy               shell32.dll                c:\windows\system32\


Restart your Windows 7 Computer and check the status. Good Luck !

One more thing, you got to run these commands on "Local Administrator's command prompt"
OR
Start -> Run -> cmd -> right click -> run as administrator
OR
Start -> Run -> cmd -> ctl+shift+Enter