What extension are the files now? Are they .exe?
Did you download any .exe or .zip files (maybe a bogus music file .wma.exe)???

If your files have changed to .exe, you're infected. Check the threads below for a bit more info

http://www.gnutellaforums.com/showth...&highlight=exe
http://www.gnutellaforums.com/showth...&highlight=exe

Apparently AVG picks this thing up (hopefully all AVs will do by now). Download AVG free, update it & scan...see if it finds a worm delf.ATB...let us know how you go.
http://free.grisoft.com/doc/avg-anti.../lng/us/tpl/v5
If you have no luck with AVG, both of those threads above have links to help sites where you can go & post a HijackThis log & get further help