Limewire is really really sketchy to use. You better have antivirus stuff running when you use it. Better yet, stay away from it with these alternatives:
Torrents: Torrents are completely p2p shared files, and dont run through a program like limewire, ares, napster, soulseek, ect. Thus, they're pretty reliable, and you have to use internet sites to actually search through them. But they work, have very very few viruses, and are most reliable for large files, like movies and games. This is a really good site to get you started:
Ares: Another p2p program that I use sometimes instead of Limewire. Some viruses, a little less well known, but has lots of users and good connections usually. I've found quite a few rare songs on it that I cant get on Limewire, so its useful just for that.
Soulseek: Never used it, but I hear its pretty good. I'm probably going to get it after I wipe my HD this weekend and start fresh and clean of Limewire.
Apparently Morpheus is still in existence, but I've never liked it much for some reason. For songs, torrents are unfortunately kinda bad, unless the site Nomensteven posted works (i'm at work, otherwise I'd be all over it right now). Try Ares I guess, or Soulseek.