Won't load past The apple logo appears with the gear thing

Um hi I'm using a macbook, i just bought it. The day before my macbook got screwed up, i installed Snow Leopard(I'm not sure if this has anything to do with this). Anyway as usual, i pressed the power button. The apple logo appears with the gear thing. I was like waiting for it to load but it just won't start! I waited more than an hour, wating for it to start but it just won't start. I tried every methods, safe mode, pressing cmd=opt=p=r and so on. But it just won't work! I really need a help here. I've got all of my school stuff on my mac.

10.0..... cheetah, MB? I don't think so (not possible)!
Need more info precise info.
Model MB?
What Software was on there (about this mac)?
How did you try to install(clean or upgrade)?
What install disc did you use (retail purchase or system specific from another mac)?
Need info!

my mac did the same thing. it started acting weird when i was running leopard. i would have a moderately small program running and it would act like i was using too much memory and overloading it, and i i'd have to do a hard restart. this happened over and over again, until i rebooted to leopard. then it seemed like everything was back to normal. then i upgraded to snow leopard. gradually, it started doing the same thing (running slow, forcing hard restart). i thought my ram might be bad so i upgraded from 2gb to 4gb of ram. it worked for about 12 hours before referring back to it's old ways. i've tried safe mode, booting without a battery (only with supply), resetting the smc, resetting the pram--every time i do this it will get past the gear screen, but that's it. i need to get this fixed! please help!!!

Ant to the OP try rebooting the PRAM on startup. Hold down the Command, Option P and R keys altogether immediately after the chimes, and keep held down until the machines sounds the chimes for the third time. Keep us posted?