[maviczap]

My PC did this, although I was running XP not Windows 7. The problems were almost indentical, I'd done all the reinstalls & formatting the drive so it was a clean install.

I took out one of the 2 memory modules, which cured the fault.

Until I took out one of the memory modules it would not boot past the black screen.

After that it was fine, until the PSU went. Replaced that and everything is hunky dory.

I know I'm referring to a PC and not a laptop, but your fault maybe a hardware fault, not software.

Also make sure all the vents are clear so the cooling fans can disipate the heat. I read about a laptop that refused to boot until the owner sucked a load of crap out of the vent ports with a hoover, which then allowed the intenal fan to blow out the rest of the carp that was stopping the fan from working