That has to suck =[
I once had a virus:
The Oompa Loompa Virus. The Oompa Loompa song was on a continuous loop and a popup would come up every now and then saying "T3H 0ompa L0ompa Owns you!!!11!!" or something like that. Plus, it would always crash my computer and then the blue screen of death would show up. IT WAS SO ANNOYING! I locked up that windows screen name by changing the password to random numbers and letters that I wouldn't remember, then made a whole new screen name and used that instead.
One day I went in and actually found the file that caused me so many problems. I deleted it and now i can use that screen name any time I want with no problems! =D
What caused it was I clicked on a link to a video on myspace and it directed me to this site with a popup saying "install microsoft blah blah to view this video" so I tried to and...never again =[