Basically this started a few months ago with my original Geforce 8500GT, it came with my PC when i bought it, had been running fine with no problems then it started acting up. windows couldn't find it, Sometimes it would run as it should then about an hour into it the sceen would flicker/flash and eventually just shut down my monitor into standby. Sometimes i would get a message saying the display adaptor had encountered a problem but had recovered, other times when i rebooted after the screen turning off it would have switched back to default onboard graphics and there was no sign of the card.
Anyway after removing it and having a look i discovered that a couple of the capacitators were leaking, figured that was the problem and it was pretty much done in...time for a new card!
Fast forward a few months, don't really have to the cash to upgrade to a better card at the moment so i picked up another 8500GT to replace the original as it had done me fine up until the problems started...
Install the new card, all is fine, windows installs it ok then asks me to reboot...get as far as the windows logo then black screen, left it for about 20 mins still nothing so i switch off and reboot...everything seems to load ok no problems.
I download the latest drivers from Nvidia site, install and reboot, everything seems to be fine...then the flickering starts again like it did the previous card and switches of the monitor, reboot and windows cant find any trace of the card...back to square one!
I removed the card, booted in safe mode and ran driver sweeper to get rid of the old drivers, put it all back in, booted up, again get to the win logo and then nothing...eventually it gives me a blue screen and reboots itself then tells me windows didn't load properly and wants to to perform a system restore which i do, windows finds the card again no problems.
Needless to say it didn't last!
I'm now thinking there could be a problem with my MB as i did upgrade my PSU to a 550 inbetween all this and since this has now happened with 2 of the same cards...i really don't have a clue!
I replaced the PSU after the first card gave up on me and before i installed the new one. Can't get the details of it at the moment as i'm at work and i can't remember off the top of my head right now the details you asked.
I did d/l and run the memtester as you suggested so i should have the results of that when i get back later hopefully.
There is nothing under where my card sits in my case so it's unlikely it leaked into anything else, never noticed any signs of anything while i was fitting the new card as i gave it a dustout while it was open.
Will post later with the PSU details and memtest results anyway
If the capacitors have gone in such a way, it MAY have been your old PSU letting the 12V rail slip, which may have affected your motherboard and other things, causing your troubles now.
The only think i can ask is to put your NEWER 8500 in a friends PC known to work just fine and see how the PC takes it. If it works as it should do, then you know that it isn't necessarily your actual graphics card that is the problem but another part of your system, possibly your motherboard.
But see how the memtest goes before anything, it could be the memory after all that text!
Well the memory seems to be solid if it's gone on for that long.
The next thing to do would be to test your newest 8500 in a friends PC that works just fine (if possible). This will help narrow down whether it's the GPU itself that's the problem or if it's something else in your system.
If it's your motherboard, you'll need a new one. Easy enough, but time consuming to take everything apart and back together again in the new one!
Well at least the memory is something i can be happy about!
Testing it in another PC could be a problem, most of my friends have upgraded to laptops these days but i will see if i can find someone who has a desktop somewhere! I only have an old Dell 2400 which i don't think has a PCIe slot in it, will check that out but im sure it doesn't...typical!
I wouldn't mind replacing the motherboard and would even take the time to put it back together but this sounds like it could be costly! I know nothing about them so could you possible point me in the right direction just for a look...wouldn't know where to start!