Computer freezes during boot-up

my computer freezes up during start-up. to solve the problem, i reformatted my pc, but it still freezes. i removed the dedicated VGA to see if it's the one causing the problem, but to no avail. PC still freezes and sometimes, when it loads, it freezes and screen turns green,black, and sometimes blue. IS this a hardware problem? how can i fix this?

MOBO:ASUS M4A78LT-M LE
RAM: 2GB
HDD: 300Gb
Processor: Athlon phenom II 965
OS : winxp pro

actions taken but didn't solve the problem:

1. installed and run CCcleaner and Registry Easy
2. removed dedicated VGA (geforce 9500)
3. reinstalled OS
4. updated graphics drivers.

can anyone help??

Hello and welcome to Tom's Hardware Forums.

Can you boot into Safe Mode by tapping Function 8 at startup and, if so, does the same behaviour happen? In your BIOS, is there any RAM set aside for the onboard graphics and, if so, can you increase that from, say, 32Mb to 64?

@saga lout : i can do safemode, but it still do the same problem..sometimes it freezes while the screen show the many lists of drivers while loading in safe mode.. i don't know anything about bios, all i know is to change the boot sequence, but can you show me how to do as what you've suggested? others say its a POWER SUPPLY ISSUE, i dont know, it has been running OK for 8 months until it does this freezing thing. I try to check my power supply once i get a chance. thank you for your reply.