intel imac won't boot up and is freezes when it does

So after about 2+ years of my 24" intel imac working flawlessly, it finally crashed today.

I was working with logic pro 8 on a project when the APP crashed. Then, the whole computer became real slow. I couldn't open anything without getting the spiraling rainbow circle for at least 3+min and even then the app wouldn't launch. So I shut down normally, which took a while.

After I left it off for about a min or so, I tried to boot again just to get stuck on the gray screen with the apple logo. I did some research on my phone (since I currently don't have internet because I'm moving this week) and found out how to reset the pram. I tried it, and this time it got all the way to the blue screen where it got stuck. I tried resetting the pram a second time to finally get to the log in screen but everything was going very very slow. Unusable type of slow. Opening a new finder window took at least 2 mins and everytime I ran my mouse across the idock, it would freeze.

I kept repeating my steps for a while. Then I inserted my os x 10 disk and tried to reinstall, but it scared me off. I don't have anything backed up, and if I lose all my data I think I would die =[

But I did make sure it was booting the correct hd and everything.

I don't know what else to do. If I'm not stuck on the gray or blue screens, my computer is so slow it finally freezes.

Help pls?

I have the 24-inch intel imac that came with the osx 10 disc (not pre-installed)
Currently I'm running 2gb of ram and I was running 10.5.8 (I think)

This might sound crazy but, I kinda got used to all of the internal noises my imac made, and something just doesn't sound right. =[

Any advice would be of great help.