Windows 7: Did I just damage my card/computer?

A friend of mine just picked up a Nvidia 550ti graphics card the other day, (his first time ever customizing a computer may I mind you) and he didnt realize he would need a new power supply (his is 250 watts) so he installed the card and booted up the PC with skyrim on ultra, after 5 mins the pc turned off and has not been turned on since, although it still powers up if you push the power button. Is it possible he has damaged his card or any other parts?

It is quite possible. Trying to draw more power than a PSU is able to provide can lead to expensive consequences. The PSU itself is likely to have been damaged and, if the regulators within have been damaged, there is a distinct possibility of other hardware failure. Of course, it is quite possible that there has been no damage to the hardware apart from the PSU (you can check this by replacing with a known good unit of sufficient capacity), but given the margin of the excess power drawn on the 250W unit, I wouldn't hold my breath. In addition, the 550ti card requires a 6-pin power connection to the card itself, and a 250W PSU is almost certainly not going to feature such a connector. In that case, the card will try to draw the power through the slot, and potentially cause damage by trying to draw more power along the motherboard tracks than they were designed for (can lead to track burnout).

Sorry to be the bearer of bad news, but consider it an expensive lesson learned.

Thanks for the quick reply, hopefully just his PSU is damaged. Assuming the motherboard tracks were damaged/burnedout, is it possible that the memory was damaged in anyway? And his powersupply did have the correct connectors which is the weird part.

by correct connectors do you mean molex conectors for 6pin adapter?

i would swap out the 550ti for what he had before and use the computer normal use and if there is no shutdowns buy a bigger power supply go for a 650 PSU and Reconnect the 550ti and Try skyrim on Ultra again

Get a 600watt psu to have extra room. I run a 6870 with a 600watt psu with no problems. I recommend corsair,I use a cx600 although a 550ti would be good with 500watts but get 600watts for extra room,mine cost me around $60usd on amazon.Also when you get the new psu and try the computer again,I would suggest doing a gpu stability test just to make sure there's nothing wrong with the card like furmark .Here shows you how to test with furmark,click the blue link and follow the instructions when your ready. If you start getting artifacts then there's something up with the video card,if you don't then it's fine and stable. Video Card - Stress Test with Furmark