What i would personally do, is download adaware www.lavasoft.com
Its the best adaware program around and voted by www.download.com
after heavy testing.
if there is still
(it happened to my friends comp) u may have no choice but to format, coz if you cant open windows explorer, u cant launch internet explorer to do online virus scanning (unless u have a good antivirus program like norton), am i right?
Do you happen to get an error message saying something like 'buffer overrun process corrupted' ?