EXPLORER.EXE corrupted or infected ?

Symptoms:- System boots properly but doesn’t load icons or start up menu. Some time gives some errors.

Cause:- This virus comes through USB Drive. If you keep USB Drive pluged into your system and restart then it infects.

Here is the procedure to remove it.
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.
Even after this if it is not working then again follow all the steps from 1 to 5 and then go to Registry Key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\Current Version\Winlogon
In that folder there is a sub called "Shell". Double click it give value "explorer.exe". if it is not there then create it.
After removal just clear the USB Drive by scanning with Good (Symantec) updated antivirus.