Nvidia 7800 GTX problem :(

I've had this awesome graphics card for five years, and it's handled anything I've thrown at it so far. Recently I had overclocked it using nTune. It worked
fine overclocked for 3 days. It ran relatively cool at 70C. Now when I run a 3D game, or anything that uses the graphics card, it works for 2 minutes, and I get
a black screen/ No signal. Usually I have to reboot my computer to get it to work again. Sometimes, I get a "The Video Adapter has stopped working and recovered" error.

I don't afford a new card right now. I'm going to get an ATI 5770 in 4 months. It's going to be a long wait if I can't play anything meanwhile
Any help please?

Idle is 50C. Before I cleaned it, was at 80C under load, but afterwards it was around 65-70 under load.

That's the first thing I tried
The funny thing is, it works fine unless I try anything but play a game. I didn't touch any drivers before and after the problem so it's probably the card

I'll try installing windows xp as a last act of desperation and see if there are any drivers that work. Is there anything I can try that might have a chance of making it work? Like flashing a new BIOS rom to the card? Could it be the PSU? I've got a 440W PSU.

There's another strange thing. I tried using the card without the power cable plugged in. I get a warning from the Nvidia control panel saying the card doesn't have
enough power, but strangely enough, games work, but at a much slower speed. Could I kill it off completely if I keep using the card without the power cable?

I have another 500W spare PSU, I will try it as soon as I can. I really liked this PSU, it's a fanless Yessico 420 ATX (Not 440 sorry )
And I don't get any funny colors or pixels, it's just working then boom black screen.

70c isn't to much better either, the G70 and G71 tend to degrade overtime at those temps on up. I suggest that you check the 12v rail and if it is below 11.5v then you do need to replace the psu or if there are large changes over a short time during use. You can easily get a cheap replacement that will outperform this card any way.

I tried another PSU. Didn't work - same problem. I'll just use the graphics card without the power cord for now. Until I get a new one. At least most games up to 2009, 2010 are playable. Even dragon age 2 is playable

Gotta love the "it ain't broke but had to fix" it posts. Bad overclock. Use enhancer to under clock the card. I'd also pull the heat sink and reapply new thermal paste. Card's probably shot anyways.

Bricked card, they don't hold up as well as modern cards at those temps. I have owned a lot of Geforce 7 era cards and had two 7600gs that I ran in sli, they would throw artifacts in the 70c range at stock despite being rock solid with a 600mhz core clock at lower temps. The three 7900gs ko were no better and were picky cards. I am a collector so I have owned a lot more cards than your usual gamer. Look around on the second hand market you Will find a cheap replacement or upgrade card.