With temperatures that high, I would suspect that the processor or motherboard may have been damaged by the extreme heat. The motherboard capacitors are particularly vulnerable to this and can be visually inspected to see that that are not showing the obvious signs of damage such as swelling, discoloration, or leaking as shown HERE. You might give them a quick inspection and see if that has any bearing on your problem.
It may also be a boot sector problem which we can try to fix using Recovery Console...providing we can get the machine to boot to the cd.
Boot to the CD. On the Welcome to Setup screen, press the R key to enter Recovery Console. Select the operating system you wish to log on to by number (usually 1) and press "Enter". When prompted for the Admin password, leave it blank and press "Enter".
At the command prompt, type fixboot and press "Enter". At the "Are you sure?" prompt, type Y and press "Enter". Once the boot sector has been written, type exit and press "Enter". Let it try to boot to Windows normally.