:(

It's my 8800GTX; first problem I've had going on 12 months now:

Sometimes it won't post; all the fans whir up (can hear the hard disks) then nothing. Other times, it posts and will boot into windows. When running windows, it will run perfectly, even under high loads.

When it booted last night:

Ran Prime95 for 3 hours, not a hitch. Cpu temps were normal

Memtest checked out ok

3D Mark 06 ran fine (4 times), expected/normal scores for the system (in comparison to online)

Hopping around in Crysis and CS:GO with everything turned up, max res/AA etc (20 to 30fps) for a total of 1.5 hours; not a hitch. No artifacts, temps/vcores reasonable according to CPU-Z/powerstrip etc

So the whole system under heavy/full load is just fine, even for long periods. WHEN it posts. If it doesn't post....well then it doesn't post :(

Swapped out the card (8800GTX) for an old HTPC card (Radeon HD4350 or some such): posts everytime, using it to type this now.

Had a quick check over the card; no loose capacitors, no cracks on the pcb, no visible dust (I clean my case out with compressed air cans (fairly) regularly), no anomalies etc.

So, it's an intermittent problem, that doesn't make any sense to me. I can:

Take off the fan/heatsink of the 8800GTX, clean very thoroughly with compressed air; even replace the old TIM with new if needed.

Or

"Bake" the card as per online instructions. I have a 4870X2 to "bake" (friends) as well....so it may be worth a shot.

Any thoughts? HELP!! :(