I have a computer problem, can someone help?

[vladittude0583]

I recently had a custom-built PC made at CompUSA about 1.5 weeks ago with these features:

Antec 1,000 Watt Power Supply Unit
nVidia nForce 680i SLi Motherboard
(x2) BFG 8800GT OC 512MB Graphics Cards in SLi Mode
4GB Corsair PC-6400 DDR2 800MHz System Memory

When I brought home the PC, everything worked fine except when I started to install all of my Norton Internet Security 2008 and some other software. Therefore, I proceeded on reinstalling my OS. After reinstalling my OS and installing all of the software again, everything was back to normal except for one thing. An screen pops-up saying that I do not have adequate power for my video cards, therefore, it forces my video cards to go to a lower performance to match the "inadequate" power supply I have installed so that the graphics cards won't crash/freeze the OS, etc.

My question is, how is this possible when everything is the same before I reinstalled the OS? I did not install any new DVD drives, HDDs, etc? Do computer "builders" manipulate the power supply or something? I did not remove any cables whatsoever because I do not even know where to begin. How could the power supply be insufficient after when it was perfectly fine before?

Can someone shed light on this?

Thanks.