I have a PC that won't boot when the temperature is below about 60F.
My problems started when it would shut itself down randomly when the graphics card was in the PCI x16 slot. I moved it to the x8 slot, and it worked for a while, so I assumed the slot on the motherboard had died. I also tried a different graphics card with the same result, so I know the problem isn't the graphics card.
But after a few days, I found that it wouldn't boot when the house was cold. The power LED would come on for a split second, but that was all. Then I would have to turn off the power supply and wait for ten seconds before I could even get the light to flicker. It would not POST and boot unless I turned up the thermostat and warmed up the house (and presumably the PC) first.
However, even when cold, it will boot if I remove the graphics adapter. This has me leaning towards the power supply as the culprit, now. But the fact that it first mattered which slot the graphics card was in gives me some doubt.
i'm thinking its a loose wire or contact on the psu. if the computers running and you wiggle some of the power wires inside the case i bet the computer will crash or shut down. it could be the heat expands a bad joint or contact just enough to make it work when the rooms hot and when you were messing with the video card you bumped the loose wire in such a way that it seemed like it was fixed for while. just a guess, good luck
Did you have the video card power connectors plugged in? If not, that can damage your motherboard or cause crashes or simply not boot at all.
My computer doesn't boot when it is too cold. It seems like it doesn't want to read from the hard drives, but mine could be a RAM, CPU, SATA controller, RAID controller, or hard drive issue. I decided to not bother troubleshooting it and I simply boot the computer into the BIOS configuration utility and wait for it to warm up before trying to boot into Windows.
sounds like a bad cap or other component on the motherboard to me... the taking time b4 you get enough power to the system, sortta suggests as much... (ie a capacitor is slow to charge)
check the motherboard for bloated or corroded components. especially round the pci-e slots.