Sounds like you have a worm/virus which copies files (or itself) into your library.
Check your system with some good up-to-date AV program as well as with some Anti-Spyware programs such as :
Spybot - Search & Destroy (FREE)

http://www.lavasoftusa.com/software/adaware/(free)

http://www.grisoft.com(good free AVG)

http://www.ewido.com(free trial which can still be used and updated after the period has ended)

http://www.ccleaner.com/download/(free)

If you can't get rid of it go here and get some free computer help:
http://norbiesworld.co.uk/computerhelp

__________________

"Never Argue With An Idiot. They Will Drag You Down To Their Level, Then Beat You With Experience"