New computer freezing randomly

My friend and I just bought new computers from newegg. With the following specs (each)

AMD Phenom II 550 BE 3.1ghz (cooler master hyper 212 for heatsink)
4 DDR3 1333 Crucial RAM
SAPPHIRE Radeon HD 4870
Rosewill PSU 600w
GIGABYTE GA-MA770T-UD3P

We put them together, installed Windows 7 Ultimate and everything was fine so we proceed to unlock.We updated the BIOS (the one suggested here http://www.youtube.com/watch?v=huKVYW4duiU) change the settings in the BIOS (Auto, hybrid) and reboot. We both succesfully unlocked the other 2 cores, we checked the temperatures and everything was smooth, so we proceed to overclock. We follow the previously posted video, in order to reach a 3.7 OC. We reboot and everything seemed OK. But a few mins later, my computer froze. I thought it was a random freeze so i restarted and keep using it. Then again froze. It randomly freezes, doesnt matter if im intensily using it or not. And then my friends computer started to freeze too.

So obviously we thought it was because of the 4 cores unlocked and the OC, but we returned the phenom processor to stock settings (3.1ghz dual core), and it kept freezing randomly "_"

And i dont have any idea of whats happening. Whats most likely happening? Windows 7 ? defective RAM / timing ? or what

Thanks in advance guys!

Hey shortstuff_mt, thanks for the repply. First of all, my RAM is the first of those 3. Second, no, i didnt reset my CMOS after returning the CPUs stock speed D:, would u mind telling me how ?

Thanks for ur time

I agree with Shortstuf on the RAM.

Make sure the timings, voltage, and frequency are set to the settings recommended by the manufacturer. Run Memtest overnight.

Memtest86+ has nothing to do with the OS. You boot from the CD and it runs outside the OS.

btw i also get a msge saying "AMD Data change...Update new data to DMI"

Yes, incorrect RAM timings can cause freezing problems. You need to run every test in Memtest86+ multiple times if you want to really test your RAM.

There will be a section in your motherboard owners manual about RAM settings. Most Gigabyte motherboards require you to press Ctrl + F1 when you first enter the BIOS to unlock some of the settings, including RAM timings.