Help! Powerbook on the fritz...

I have a powerbook that is a little over a year old (and thus no longer under warrantly).

Last night, I attempted to open up limewire and then limewire wouldn't open, it just froze. My entire computer did, so I turned it off the manual way, and when I rebooted my computer, none of the programs (mail, safari, iphoto, etc...) would open.

Now this morning, it takes so long to open programs - that little rainbow circle keeps spinning. It's like the computer is trying to open the programs, but nothing works!

When I tried to open iphoto, I got a message that said there was no library. This isn't true, I had over 500 photos. Yikes!

PLEASE, if anyone can give me any advice, I will be eternally grateful! What should I do? What do you think happened?

Powerbook G4 12" Mac OS X (10.4.8)