If you dont get a chime, which I didnt hear one, its very possible the sound IC is bad or traces to it are broken. 

Elfin: your not going to be able to watch the voltage rails with a DMM easily with popping like its doing, the voltage fluctuations would be too fast. You would need a decent oscilloscope to watch the rails for spikes. the spikes can cause the pops. especially if one of the filter caps in the PS didnt solder well, or anything really. Also any spikes in the 5V rail will glitch the CPU and cause all kinds of functionality madness. 

The DMM has a fairly slow response time unless its a high end fluke. If the DMM catches voltage fluctuations then the power supply is grossly faulty and you would be lucky the machine runs at all.