He also said there were a bunch of cables. One of them is 24-pin, but what are the others?

That's a Dell XPS so the PSU cables should be standard, the only things that wouldn't be are things like front panel USB and such.

There's a 24 and 8 pin.

Then you're good to go. PSU and GPU, hope it works out for you. Something better than a power strip, too. An actual surge protector at least.

Had to buy http://www.amazon.com/gp/product/B003XU78OA/ref=oss_product that GPU, because the other doesn't ship outside the U.S

Parts have arrived.

BIG problem. Installed PSU and GPU but when I turn it on the fans spin up and then everything just stops with no beep code. But the light on the motherboard and on the Ethernet port still stay on.

Are all the requisite power cords installed, especially the large and small ones that go to the motherboard?

Yes Kerm, they are.

Computer came back from the repair place. Turns out one of the small connectors were in the wrong place....

you mean the GPU power connectors? >_<

lol no. We had to take the motherboard out to get all the power cables from the old PSU out, stupid Dell.

You said you had 4gb of ram windows 32bit only supports up to 3gb. This won't fix your problem ,but it was nagging me a-lot to point it out. Have you tried flashing your bios? If not give it a try won't hurt unless you mess it up and it's free. On the super small chance that helps I would get a bootable linux live iso and boot off of that just to test . If you can get the same error it's allmost guranteed to be hardware since two OS's had the same error.

The problems fixed, every things fine. My computer came with Windows Vista 32-bit and upgrading to 7 64-bit means having to reinstall everything which I couldn't be bothered doing at the time.

Oh, that's great to hear. I'm a little vague on what actually fixed the problems you were having, though.

to install the new PSU we had to take the old PSU which meant disconnecting everything. Dell decided they would have the 24-pin chord go under the motherboard and then up and over into the socket. That meant we had to disconnect the motherboard and take it out to get the chord out. We must have put a cable in the wrong spot or ordered some cables wrongly, that's what I remember being told what the repair shop person said.

Ah, that makes sense, thanks for the clarification. Well, I hope you don't have any more hardware problems, but if you do, we'll be here.