Macbook Pro unable to get pass the Log in Screen.

Hey hope someone can help.

Okay so last night I was using Windows, I shut down, then a few hours later I switched it on to go onto my Mac, but it took forever, I left it though and eventually I got to the log in screen, I entered my password and it was loading then the screen went blue/gray (not sure I think both) and went back into the log in screen again... I did this numerous times before giving up and shutting down. Went to sleep, woke up and resumed this...so I decided to see if I could log into my windows, which it did just fine, I'm on windows typing this right now.

I have run the apple hardware test, extended too, and I have recieved the error code: 4SNS/1/40000000:Th2H-63.000 (No idea what that is)

I have also tried booting from my start up disk that came with my Mac. It gives me the Apple logo on the gray screen then ejects my disc, gives me this long story... kind of goes: panic (cpu 0 caller 0x00431da3):"unable to blah blah... Tells me to restart or shutdown.

I looked at my disc and I think its cracked, So I have to get that replaced.

I think I have to archive and install, I really don't want to lose my music, as I haven't backed it up. 400 songs or so nothing much, I'm not worried about the other stuff as that is all backed up.

Long story short can someone tell me what's going on with my Mac? why am I still able to use windows fine? Has windows done a hit on Mac OS? lol. Is the solution to replace my install disc at Apple? I really don't know, any help would be greatly appreciated thanks, I'm just too tired and can't Google anymore :P

(I have a small partion of 32GB dedicated to Windows Vista.)