Just because your AV didn't detect it doesn't mean you aren't infected...
These people that create these viruses are very clever and AV's are not infallible...
Could you just humour me and do a self check, if you feel you don't want to go to one of those sites to get diagnosed...
Create your log and check it here...
http://www.castlecops.com/HijackThis.html
If your fiance is a computer networking technician what does he think could cause an mp3 to turn into a zip file ???
Also what other file extensions have you downloaded in the past?? or have you only ever downloaded mp3s....Also have you ever downloaded that "urgent limewire update" ......