I'm a new Mac user (PowerBook G4) and i've downloaded LimeWire 3 times now and it doesn't want to work. I get the disk image, downloaded it, got the LimeWire icon, but when I click on the icon it bounces 2 or 3 times then disappear. Please help 
You are out of luck with G4, look at the their website for system requirements:
Minimum requirements:
OS X 10.5 64 bit Intel only, OS X 10.6 32 and 64 bit
You can either try to find a very old version, if they had any for G4. But Dont worry if you cant use it, I had latest version on my Intel MBP and it slowed system down so much that I could barely use it. Lags were everywhere so I deleted it.
Bittorrent is my advice.
Ok 1st limewire network (not the program itself) is fully of viruses and spyware.
to those asking what is good about it? To download music (song by song) in case you do no want a whole album.
Last time I installed limewire pro 2 months ago, my mac became slowly unusable when it was working so I had to force quit it.
Honestly, I have been using BiTTorrent to fulfil my needs for more than 6 years and I still do not think there will be any better thing in the future.
You are out of luck with G4, look at the their website for system requirements:
Minimum requirements:
OS X 10.5 64 bit Intel only, OS X 10.6 32 and 64 bit
You can either try to find a very old version, if they had any for G4. But Dont worry if you cant use it, I had latest version on my Intel MBP and it slowed system down so much that I could barely use it. Lags were everywhere so I deleted it.
Bittorrent is my advice.