Why would you want to launch stupid music? Real music files are about 4 megs or more, but the spam/virus stuff downloads much quicker since it pretends to be a music file just to get you to download it. You're lucky to be on mac, or you'd likely end up with the "german porn dialler" (search for this to see more). DON'T SHARE those spam files or you'll be hated!

It's a good idea to check out all the files you download, and only leave tested files in your shared folder. The junk/incomplete/corrupt stuff propogates so quickly because it's small and too many people download anything that might look interesting.