For IIS6 web server that is hosting two application pools. Occasionally, one of the w3wp processes will spike the CPU for a while, and both app pools seem to suffer the consequences.
Goto cmd window then type c:\windows\system32\cscript c:\windows\system32\iisapp.vbs
For IIS7 you need to use APPCMD from %systemroot%\system32\inetsrv\ as an administrator
%systemroot%\system32\inetsrv\appcmd list wp