HP Pavilion dv6500t GPU problem?

Hello,
I'm having a problem with my HP pavilion dv6500t laptop equiped with Nvidia geforce 8400.
The DVD R stopped reading/writing a few weeks ago, and 1.5 weeks ago, I kept getting bluescreens. 1 Week ago, my screen started to turn off when watching video, etc. Tried to fix it by installing various drivers, chipset, etc. Wouldn't work, driver kept getting me code 43, or would just give me a blank screen after windows loading screen, or would stay at 4 bit, low resolution.
I got tired of it and installed fresh XP using USB stick. Installed GPU driver, and all seemed to work well until screen started to flicker like crazy after about 5 min. of use. mouse would move around, but computer won't respond. Tried to change the driver, and would againg get the blank screen problems.
Just now, I restarted it *without installing new driver' and it seemed to work, until it flickered and froze again.

What the hell's wrong with my laptop? so tired of this...
I really need your help...