Nvidia Video Card Crashes: Software or Hardware?

I've had my GTX 295 for awhile now, and recently, within the past couple of months, I get these random crashes when I'm watching a video or playing a game.

How it happens:
Everything will just freeze, then un-freeze; I do not get a BSOD. If I'm watching a video on a media player or on Youtube, it will just go black, and I'll have to restart it. With games, it will freeze, bring me back to Windows, show the error in the bottom right (Display driver stopped responding and has recovered), and the game will still be running, but minimized. I can then click on the game and continue playing until it happens again.

I've tried manually updating the drivers by uninstalling, removing leftovers in safemode with Driver Sweeper, then installing the latest driver. No help.

I've also tried editing the registry entry by adding the "TdrDelay" line in the GraphicsDrivers directory and setting the value to 0. At first, I set the value to 10, and it just amplified the problem. Setting it to 0 calmed the problem down A LOT, but it will still freeze, and when it does, the entire computer freezes and I have to restart the rig.

Also, all temps are going to ~180F (84C) on the gpu running Furmark

I would really just like to narrow this down to a hardware or software problem, so I can have an idea as to where to go next; any help is greatly appreciated, please let me know if you need any other information.

-jb

Rig:
AMD 965BE
Asus M4A79T Deluxe
GTX 295
1000w PSU
Win7 Ult x64


Error Message:
Description
A problem with your video hardware caused Windows to stop working correctly.

Problem signature
Problem Event Name: LiveKernelEvent
OS Version: 6.1.7600.2.0.0.256.1
Locale ID: 1033

Extra information about the problem
BCCode: 117
BCP1: FFFFFA8007E304E0
BCP2: FFFFF88013F58354
BCP3: 0000000000000000
BCP4: 0000000000000000
OS Version: 6_1_7600
Service Pack: 0_0
Product: 256_1
Bucket ID: X64_0x117_DxgKdxFailed_IMAGE_nvlddmkm.sys
Server information: cfcdadbd-6ff9-48fd-a80f-610f62e4e0e5

STOP 0x117 is very similar to STOP 0x116 - and here's the link for troubleshooting it: STOP 0x116: VIDEO_TDR_ERROR troubleshooting

You've updated the drivers, you've tested w/Furmark. Have you checked to ensure that the card is getting enough power, that it's fan is working, and that the cooler is clear of dust/obstructions?

If you've done all that, then the next step is to try another video card. If you don't have one, see if you can borrow one. Worst case, purchase one at a place that will allow you to return it for a full refund.