New Build Freezing/Crashing

[teslaxero]

Recently built a new pc for the wife. Everything has been running fine for about a month, but recently it has been freezing up and/or crashing. Sometimes it just locks up and has to be restarted, sometimes it blue screens. I am using Kaspersky internet security 2011, so I was hesitant to jump to virus. It felt like a driver conflict or something to me and the issues seemed to line up with an automatic windows update. Being as there was hardly an information on the new build I decided to reformat and do a fresh install. But now it is freezing up during the new install so its seems like hardware.

Build info:
MOBO: ASUS M4A79XTD EVO
CPU: AMD ATH II X4 645 3.1G AM3
MEM: 2x2GB GSkill DDR3 1600
HD: WD 500GB Caviar Black
GPU: Sapphire HD5770
PSU: Coolermaster 550w
OS: Win7

What kind of hardware problems could be causing these systoms? And why would it occur after a month of flawless operation? As I said it has been reformatted and is freezing up during the windows installation now.

UPDATE: NO overclocking was done to the rig

 

[teslaxero]

I managed to reinstall windows and the problem is still occuring. After several crashes or freezes it will have a period of long stability lasting several hours. I'm at a loss here it doesn't seem be a load thats causing the crashes.

 

[teslaxero]

I still need help with this if anyone has any ideas

 

[majin ssj eric]

Memory is the most likely offender here in my opinion. You could run a mem-test or try just one of your RAM sticks at a time and see if that solves the instability issue...

 

[teslaxero]

I did run a mem test and found failures on one stick, but after removing it and using just a single stick that passed the problem is still occuring.

New Info, got a BSoD with BAD_POOL_HEADER 0x00000019

what is this problem?