Comp crashing during gameplay after upgrade to GTX 560 Ti

Hey everyone, Quite recently i purchased a Gigabyte Nvidia Geforce 560ti Graphics card.

I'm not quite sure whats going on, and before i go spending money i'd like to get some other peoples opinions as people i've asked are not to sure.

My computer specs are:
(not completely sure on the motherboard but its Asus.)
4gbs of ram
Intel i5 2500
Gigabyte GTX560ti
western digital harddrive.
And a 550wat generic powersupply

Sorry if those a vague, its very late, and i've been trying to work out what the issue is.

I hadn't occured these crashes before upgrading to the 560ti.
My prior card was the nvidia 210. (not the gtx) it was a heatsink model if that helps

With the crashes what happens is i'll be playing a game, such as skyrim, or even dungeon defenders, and after about 10 minutes my computer shuts off as if it lost power, and instantly reboots, without me touching it. could it be an issue with my power supply?

i've monitered the heat of the card and it seems to max around 60-65 degrees celcius. if any body could help it would be appreciated.
 
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