|"...sat there for maybe half an hour .."|
"...reconnected everything and it just worked."
"After another 8-10 it flickered off again "
Obviously the card is malfunctioning after it, and/or the computer in general, has warmed up some.
"I've tried taking out the video card and putting it back in."
If you have checked out and tried everything I mentioned in response 1 regarding the card and the cpu fan and heatsink and they're OK, your card is probably damaged. If you have doubts about the fan on the card, you could try replacing that.
Otherwise, the only other thing I can think of that might cause your problem is a poor connection in your ram slots.
See response 2 in this - try cleaning the contacts on the ram modules, and making sure the modules are properly seated:
" ,,,,it seemed awfully coincidental to have it happen all of a sudden the day i put in a 850W psu to discover that my 500W psu was faulty. "
Did you remove the AC power to the case/PS at ALL times?
ATX power supplies are always powering ATX mboards in some places, including some contacts in the ram and card slots, even when the computer is not running, as long as the PS is connected to the mboard, the switch on the PS is on if it has a switch, and the PS is receiving live AC power.
You should ALWAYS disconnect the AC power to the case/PS whenever you make any changes to connections inside the case or install or remove components inside the case, including simply connection power to the drives.
If you didn't do that at ANY point, you can easily damage anything connected to the mboard or to the PS, and/or the PS.
If the video card was not all the way down in it's slot at any time when the computer was running, or possibly even if it wasn't running if the PS had live AC power, the card could have been damaged.
This alone could have damaged the card...
" I unplugged my monitor and plugged it back in because I thought that's what you do to solve problems."
"Could it be with the wattage of the PSU"
Certainly not regarding the Thermaltake 850 watt PS.
The 9800GT video card requiring a minimum 400 watt PS be on the system would have loaded the 500 watt OCZ PS to as much as 80% , or more, of it's capacity, all the time - it should have been able to handle that.
A look on the web finds the OCZ PSs have a decent 3 year warranty and a decent reputation .
However, there is always a percentage of PSs that malfunction for whatever reason - it's just a lot less likely to happen if it's a good quality PS.
Are you sure it's a 9800GT?
e.g. a 9800GTX chipset requires a minimum 450 watt PS be on the system, and that would have loaded the 500 watt PS to as much as 90%, or more, all the time.
"As for knowing I have the right drivers and BIOS (what are BIOS?), how do I go about doing that?"
If the video works ok when the computer has had a chance to cool, your problem has got absolutely nothing to do with drivers or the bios version.
Drivers cannot normally cause your symptoms in any case - it sounds like your problem is a hardware problem, not a software problem, in any case. If once the video malfunctions it doesn't work properly BEFORE Windows starts to load when you try booting or re-booting the computer, it can't possibly be caused by anything on the hard drive.
If the video card worked fine previously with the present bios version, the problem cannot have been caused by the bios version.
Flashing the bios is NOT a cure-all !
NEVER flash the bios unless you find specific info such as in release notes where you download bios updates, or in cpu support info for the model, that it will cure the exact problem you're having.