Have you checked the motherboard for any signs of damage? blown caps etc? I would normally just say this is what happens when you don't do proper stability testing (unstable systems are bound to crash eventually) but the noise you describe sounds a bit strange. If you don't have an internal PC speaker (old school!) then I'd suspect the PSU would be the prime source of a noise like that?
Did the noise appear after the crash? or before?
Havent checked the board for any damage mate as its a pain in my knees etc to get down there and have a look etc, lol, got kinda knackered knees man, lol

There is no speaker in the base unit at all.
And the sound occurred instantly at the point of the crash, and it kept on buzzing away and a frozen screen until I switched it off using the off button on the base unit too, don't know if that helps ya any ?
