Yeah I agree with OLD SHEP as I have had quite a few trojans on my PC using P2P networks so I have stopped using them now as they are not worth the hassle.
The 'brilliant digital' trojan that I accidentally downloaded from KaZaA Lite messed up my internet connection with DNS server errors.
I couldn't delete it either (even in SAFE MODE) as I kept getting a message that the MP3 file was in use by another program.
I could not get my internet connection back even using system restore so I was lucky to have made a backup using the excellent Drive Image 7 disk cloning program!
It was P2P networks that caused this as since restoring my backup and NOT bothering with file sharing networks I have had NO problems and that was a few weeks ago!