you cannot get viruses from mp3 files. they are not executable. beware of files that are executable like .EXE, .COM, .VBS, .DLL, .SCR, etc..

small list of safe extensions:

.mp3
.wav
.mov
.zip / .rar / .tar/.gz (but beware of the contents inside archive)
.html (but beware of the contents. you never know what script could be hidden in one of these.)
.pdf
.ogg
.mpg ; .mpeg
.avi
.jpg ; .jpeg
.gif
.png
.bin/.cue (beware of contents inside archive)


-= Extensions I would never download unless im absolutely, positively sure that it was a clean file =-

.exe
.zip
.dll
.com
.wma
.wmv
.bat
.vbs
.html
.sys / .ini / .reg / .key (harmless really, but it could have a dangerous script inside)

-=-=-=-=-=-

i know i am missing alot of other extensions, but eh. basically you should limit your downloading to only media files and archives. and avoid .wma / .wmv files at all cost. and always keep your antivirus definitions up-to-date (if you dont have a virus scanner, i recommend AVG, get it for free here: (free.grisoft.com).