First of all, I'm not a Vista user

Did you download a file just before this started happening? If so, can you remember which file it was? Try deleting that file from your computer. The same kind of thing has happened to XP users after downloading a corrupt file. Deleting the file was the fix for one person, from what I can remember, another person fixed the problem by running AVG Free AV.
AVG free
It wouldn't hurt to run an AV scan, just to be safe.

If you didn't download any files before this started happening, have a look at these & see whether anything helps.
windows explorer has stopped working, windows explorer is restarting LOOP! - TechNet Forums
Windows Explorer Stopped Working - Windows BBS
windows explorer has stopped working, windows explorer is restarting LOOP! - TechNet Forums
windows explorer has stopped working? - Tech Support Guy Forums

That's just a bit of info I found by using Google. Try searching for more...type in Windows Explorer has stopped working Vista...see whether you can find more info to help. Otherwise, a Vista user here might be able to help more.