Mac problem

So I have a MacBook, and I have had it since about august, it has had no problems whatsoever. A couple of months ago, I uploaded Leopard onto it. Anyways, earlier today, it randomly froze, but I was still able to maneuver the mouse, but everything else on the screen was frozen. My dock was just about to come up from being invisible below my screen, and got frozen so I could barely see it. So I decided to turn the computer off, because I could not do anything else. Now, everytime I try to reboot the Mac, it won't leave the white loading screen, with the mac apple, and the spinning loading circle below it. Actually, just now, it loaded up a blue screen, but is now stuck there. Does anyone have any advice on how I could fix this? Any help would be appreciated, thanks.

Pop your Tiger or Leopard DVD in and try and reboot from the disc. If it boots, go to Utilities and run Repair Disk from Disc Utilities and see if there are any HDD problems and repair if necessary.

Let's know how you go so far?