World of Freeze! Please help...Follow

I have been through the gauntlet with my recent purchase from Dell... In short, I was sent a computer plagued with problems, in which I returned for a replacement computer. This 'replacement' computer, runs more stable and has had only one blue screen due to an anti-virus running while downloading Everquest 2. However, since I have made a return to the World of Warcraft... The computer has frozen on me twice now while playing!!!

My computer specs(Dell XPS 720):

- 2.93 Ghz Intel Quad-Core (2.66ghz factory overclocked)
- 4GB Ram (667mhz) (2.75GB shows)
- 2 Nvidia 8800 GTX graphic cards (SLI-disabled because it makes things worse)
- Windows XP (Media Center Edition)

A few days ago, I was playing World of Warcraft (about 4 hours of playing in), when everything froze! I was unable to exit the game and return to windows, forcing me to turn the computer off. This same thing happend last night, again, about 4 hours into playing!

Could this be an overheating issue occuring with the CPU? My Graphic cards are running pretty cool, and never get above 70 degrees C usually. However, I am not sure about the CPU... At this point I am frustrated with this computer, and am stuck with it! I will never buy another computer from DELL again...

If any of you may have any thoughts, suggestions, or comments, I would be greatful for your help! Thank you in advance!

I have already tried, believe me! Dell claimed that I had 21 days to return the product for a full refund... They claimed I was on day 42! That's day 42 from the time I MADE the purchase online!!! That doesnt account for the processing time, shipping time (at least two weeks for both computers), and that the original computer didn't even work!

I unfortunatley think I am screwed... I also spent about 200 extra dollars, on an extended warranty, with In-home care... Dell also refused to send a technician unless they sent me through more trouble shooting, and self-tests on the hardware in search of an error that would suggest hardware malfunction...

In short, I received two malfunctioning machines from dell, and they refused to give me a refund or send a technician. It is beyond me, why I have to troubleshoot in the first place, spending my time on a machine that they built!