Windows explorer is not opening or explorer.exe is not running

If on booting, exlporer.exe does not run, no need to format. This was discussed before here.

do this,
copy the I386 folder from windows setup cd to you HDD.

while windows is booting, press F8 key and ADVANCED start up option will appear.
select SAFE MODE WITH COMMAND PROMPT.

navigate to your windows directory.
then rename explorer.exe to explorer.bak or something.
Now go to the i386 directory.

use this command :

expand Explorer.ex_ x:\windows
// where 'x' is your drive letter where windows is installed.

now restart your PC and check the result.