I have fixed a LOT of computers that had Limewire installed. Limewire is a conduit for viruses and spyware. If you decide to use it, make sure that you are running a good, up to date, virus checker such as Norton or McAfee. Also SpyBot and/or Ad Aware are worth installing, as they will manage the spyware issues.
Limewire is a piece of software you download so you can download music for free. It is safe to use but it is illegal, but people use it anyway. I don't use it, but you could use http://funadvice.com/r/3jthf1i22g or just buy the music on itunes. It doesn't even cost much.
Limewire is not completely safe i hate to spoil the mood. If you do download it make sure you have a VERY good virus protection on your computer. Limewire is the reason my laptop is no longer usable.
limewire allows you to download movies, pictures, music, and other stuff for free. i use it all the time and is safe.