HDD, Mobo, Ram, hardly ever cpu.
Dont suppose you have a spare HD lying around you can format and try and instal windose on, before you format the exisitng one?
Make sure the ram modules are firmly secured, take them out and replace them again, just in case.
What you describe above was what I had, and it was my mobo that died, not the HDD, I could get into the bios is about all towards the end before nothing at all, just constant power on power off cycles.
So in an attempt to save your data on the existing drive before you go ahead with a reinstal its worth a trying to see if another drive will function, if you can.
Good luck.