Windows 7 gaming laptop problem

I recently just put windows 7 professional rtm 64bit on my laptop
when i would either play half life and half life 2 games for like a minute or sometimes a few seconds my computer freezes up and crashes.

i have 2gb of ram ddr2 800mhz
cpu t9600
9600mgt 512mb ddr3
resolution is 1680x1050

i have tried everything it would always get a blue screen and uninstall itunes i thought that was the problem but no.. i even put a new batch of arctic silver on both the gpu and cpu.. i can just surf and do notes on word i just cant do any gaming for some reason does anyone have the same problem or anyway to fix it?