I hope this is not an inappropriate forum.
I have a bootup problem that has me stumped. I have a desktop (Compaq Presario SR1750NX, AMD Athlon 64, Asus ABAE-LE motherboard, onboard ATI Radeon Express video, 3G RAM, 1.5TB + 500G disk) built in 2005. In the last 6 months or so, it has had 3 or 4 instances where, after power had been completely removed (plug pulled, not just shutdown), for >12 Hrs, the system would not come back up when it was powered up again. Lights would come on, fans would spin, but there was no other activity - absolutely no video, not even the pre-boot splash screen, no POST indication, even the soft power off didn't work.
When it was left powered on for several hours, it would suddenly boot and everything would be fine.
The first time it occurred, I replaced and upgraded the power supply, and still had the same results, so I don't think it's the PS.
It has occurred again following my upgrade last weekend to Win7 RTM. But this time, it's not coming back, even when left on for >24 Hrs.
When it first happened after the upgrade, I had been thinking maybe the CMOS battery had reached it's shelf life, so I replaced that. And it did come up a couple hours later. But then it went into a sleep state after being up for a while, and would not come back out of it. And it hasn't been backup since then.