www.divx.com usually plays most videos. I just wanted to mention that I remember my brothers had that same problem, their notepad.exe seemed to have disappeared. Unfortunetly I dont remember how I fixed this problem for them. I'm pretty sure it was caused by some sort of adware program and did the same for your wmp. I cant find the exact site I read to fix my brothers comp but this site may be able to help you http://www.spywareinfo.com/~merijn/winfiles.html

If this doesnt work for you I would be more than happy to do some more research for you on how to fix this problem.

Cheers