Ouch! When something stresses the mobo enough to provide sound effects...you got a problem. There's very likely a broken trace or "popped" connection in the North Bridge circuitry. This would cause exactly the problems you describe.
may of heard a small sort of snapping noise
There's a lot to be said for building your own...I've built all my personal machines for the last ten years. They've all proven to be very reliable and resilient. Having your own operating system disk is another bonus...you have more options on disk than most OEM disks provide. Dollar for dollar, you'll get twice the machine and half the headaches for the same price by building your own.
Check out our System Building forum. That's a real good way to get to know what works and what doesn't.
I think we can safely say this mystery is solved.......buddy killed the North Bridge........