New Graphics card system keeps re-booting

Hi Guys,

I have just been completing some new system upgrades on my rig and having problems with the graphics card.

I recently purchased a Maximus 3 Formula M/Board, Core i5 750 CPU, Crossair DDR3 1333Mhz RAM and NvidiaGTX275. Installation went all OK, unitll I tried my new (2nd hand) GPU. The GPU is a 275GTX and when installed all appears to be fine, untill I game. I have only tried Modern Warfare 3 and after about 10mins, my machine powers off instantly and then proceeds to boot up again. I have tried re-installing the GPU and connections but no change. The card is fully working as have seen it in use prior to purchase, it has never been overclocked and is not in my rig. I have the latest drivers installed and temps never go above 60 degrees when gaming.

The only thing I can think of is my power supply. I am have not very well known brand of power supply but has served me well. I had previously been running the same rig but with a NVidia 9600GT GPU instead and it worked with no faults at all, I have even had it running with x2 9600GT's in SLi and no power problems.

I can boot happily into Windows 7 64bit and surf the internet but as soon as I game, my machine dies and re-boots.

How can I be sure if it the power supply? If not, what else?

What is your Power Supply? I think it's at fault here. List full model please. By the way, the longer you used your PSU, the more its' capacitors aged, so it might have been just enough for 9600, but GTX 275 is more power hungry.

It's your power supply 100%. It has only 312 Amps (12*26) on 12V rail, and GTX 275 alone may eat up 251 Amps when it gets to load.
http://www.tomshardware.com/review [...] 66-14.html
Not much left for your CPU and rest of the system, huh?

Anyway, I'd suggest you get a quality brand PSU, which will serve you a long time.
Quality means Antec, Corsair, Seasonic or XFX.

http://www.newegg.com/Product/Prod [...] 20tx%20650

Something like that one has 53Amps on 12V rail, and it's more than double of your current one.

I guess you could find a good PSU for $70 for GTX 275, but I doubt you could find cheaper one.