XPS 600 Motherboard sucks....anyone relate?

Is there any hope for my XPS 600 that I have used infrequently? After 1.5 years it's fried. I changed the ram, cmos battery...I now get 6 beeps...2 long one short, then 2 long one short...I hear the fan when it is on, no screen view...nothing will load...

I am with you on the motherboard issue here is my situtation...

I have had lots of problems with my xps 600 since the day I took it out of the box it in came in. Working with Dell I was able to resolve a lot of these problems (bad hard drive etc) accept for one major problem.

The xps 600 is just a little over 3 years old and I am on my 3rd Nividia 6800 graphics card. My video card after about a year fails. The error I get is a failure to write/read to the video card memory. Although Dell support tries very hard not to send me a new video card (costly item) with lots of wrangling they eventually do as I am under full warranty. The card arrives it gets installed and the PC works absolutely perfect for about a year. Then the video card goes out again.
The problem is my warranty is expiring and dell wants about $150 to extend the warranty. Being that video cards are so expensive I may have to do this.

However, the best option would be to fix why the video cards are breaking. I think there is a problem with the motherboard. I think maybe there is a voltage problem on motherboard which is breaking my video card but I have no way to prove this to Dell support so I can get a new motherboard. Does anyone know of a way to easily and cheaply test a motherboard for voltage issues?
Also this is NOT an environmental issue. I have an IMAC and HP computer and HP printer in the same location and they have no problems. I have a costly UPS so no surges or shortfalls and the area has great air condtioning. In my house with my kids and wife we have 4 other computers and none have any problems except for the XPS.

In the long run with the cost of video cards this would save Dell a lot of money to really solve the problem...but the diagnostics they have me run never report motherboard problems but I don't think their diags test deeply enough. Any thoughts out there? I paid way too much money and invested way to much time to simply give up. All suggestions are welcome!