Computer FREEZES while playing SOME games

[tevoyatumbar]

Hi, I am new to these forums. I bought a new built computer, here are the specs (from speccy):

OS:
MS Windows 7 Ultimate 64-bit SP1
CPU
AMD Phenom II X4 955 44 °C
Deneb 45nm Tecnología
RAM
4,00 GB único-Canal DDR3 @ 668MHz (9-9-9-24)
Motherboard
ASUSTeK Computer INC. M4A87TD/USB3 (AM3) 43 °C
Graphics
SyncMaster (1440x900@60Hz)
ATI Radeon HD 4600 Series (XFX Pine Group) 42 °C
Hard drives:
488GB Western Digital WDC WD5000AAKX-001CA0 ATA Device (SATA) 33 °C
Optical Units:
HL-DT-ST DVDRAM GH22NS50 ATA Device
DTSoftBusCd00
Audio
Dispositivo de High Definition Audio

While playing Dirt 3, Call of duty 4, Mw2, after about 15 to one hour of playing, my monitor turns off, its power light starts blinking, i still hear sounds from the game for about 5 seconds, then it freezes, kind of like a scratched cd.

However, this doesn't happen with Battlefield Bad company 2.

I searched a lot online, and there are millions of different answers, and it's very confusing. Some people say it's RAM related, other say its PSU related, other say it's Graphics related, other say its Heating related, etc.

If i need to specify anything else of my computer, i will. I do not have any viruses, i am 99% sure it's hardware related. Thanks

 

[f1zz1e]

Only game i freeze on is battlefield bad company 2, always crashes for me, you have the latest drivers/bios etc?