Computer unstable after 8800GT volt mod

Yesterday I had to just try overclock my 8800GT card when I reached the border. So I thought if I could modify volts as I have seen others do it. I found a guide on the web and began to rush into it. I put the voltage of 1.10 out NiBiTor that came with the package in the link and then flash card. It works fine for normal use, but then I would get it up on the 700 core and 999 memory or so, giving both ATITool artifacts and sometimes freezes my computer too full and I need to take power.

Is there anyone who knows about my problem or what mistakes I have committed? Could it be a power supply of poor quality?

Specs:

ABIT Fatal1ty FP-IN9 SLI
Core 2 Duo E4600 2 MB
Geil Black Dragon 2 x 2 GB
3312BLA NorthQ Giant UFO
750 W power supply (Can not remember the brand, do not think this is something known)
Inno3D 8800GT

If your comp freezes, so there you go too fast! Possibly the card gets too hot!

My advice is that you increase it only a few MHz at a time and test the minimum 10min each time to get the card up in temperature.

I am 100% sure that it is not due to heat, the Everest and Rivatuner both says that it only comes up to 55-56 during the ATITool artifact scan.

It is with that other cards are better. Is it because I got a bad chip of the card, not clock as high or is it because it is an older version of the chip. As in the example processor e8400 E0

Take any cooler and see what ram is getting on your card so you can get a better idea of what they can do in MHz and how much power you have to give them.