This has been answered lots of times before, but since I like you sig I'll make an exeption

About the legality here is one thread to get you started

(Click on link ) http://www.gnutellaforums.com/showthread.php?t=61641

Viruses:

http://www.gnutellaforums.com/showthread.php?t=41432

I can't tell you whether you should download Limewire or not. That's completely up to you. For more info in limewire use the forum search and read some of the Sticky's at the top of every section.

Cheers

Sleepless