Distorted Pixels, then Blacks Screens

Last night, I was playing Garry's Mod, when my two monitors went black. Usually, this just means my graphics driver crashed, or the game crashed (in both scenarios I can get to my desktop). My monitors were both in sleep mode, and I couldn't get them to display anything. I restarted my computer about 10 times over the course of about 2 hours, but each time, my monitors would randomly have distorted pixels that came and went, then eventually blacked out, leaving a hard shutdown as my only way out. Sometimes I'd make it to my desktop and have about 10 minutes before I got distorted pixels and lost monitor signals, sometimes it would happen on the loading screen. On my desktop, pushing the windows key, then using the arrow key to tab over to the shutdown button, then pushing enter to shutdown, wouldn't do anything. I just had to hold the power button. This morning I had no issues for about 20 minutes, then I had to leave, so I shutdown my computer and took my graphics card with me to see if the IT department could help. The only thing the guy said was that he could check to see if they had another graphics card of the same type in their sea container out back. I got home today, put the card back into the computer, and started having the same problem again. I've had the same computer for about a year, and I've had a second monitor for about 6 months.

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Nvidia GeForce 8800 GT (graphics card)

4GB RAM

Windows 7 64 bit

Intel Core 2 (typing this out on my iPad, so I'm not sure what the rest of that is)

Left monitor: Dell 1440x900

Right monitor: AOC 1920x1080

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I'm not really techy, but I followed an IT guy around for a summer, plus I've had tons of tech problems that I've been involved in solving.