Explorer.exe error

I am having Windows 2000 professional, in this
when i click any folder in the desktop, the following error has appeared :

Program Error :

” explorer.exe has generated errors
will be closed by windows
you will need restart the program ”
i have expanded the explorer.exe file from i386 folder to the c:\WINNT, but no result.

Requesting you to help me in this issue.

Thanks
Manikandan.V
India