Generic power supplies have a tendency to surge when they fail, which may fry other components. Also, a cheaply made power supply may not supply enough power to all the components, especially during the boot, which gradually damages them as they are power starved. This normally causes odd behavior in a system, primarily with the AGP port and 3.3v video cards, which share the power with the +5v rail.
If you are going to overclock, Papa, make sure that you have a really good cooling solution, and a PSU that can handle the power requirements of your system with some redundancy. A good, heavy-duty PSU should run at no more than 70% at full load, and with an AMD system, it's best for it to have dual-fans for additional cooling.
I'd say that a combination of an inadequate PSU and the overclocking caused your problem. Most of the time, for an overclocked system to be stable, the voltages have to be increased on certain components (as I am sure you are aware), and that probably cause the PSU to fail even faster.
I wouldn't have run that system on anything less than 430W, and if overclocking, a 550W. Check out Enermax, PC Power & Cooling, Sparkle, and Leadman for good PSU's. I'd suggest you avoid the standard OEM Antec PSU's for overclocking, and the higher wattage PSU's from the same company have a higher RMA rate than the older 300W models ... which is inadequate for your purposes, at any rate.
With the mobo and the hard drives ruined, check all other devices for damage before using them, especially the memory and the video card.
Sorry this happened to you ... I know how it feels.
Toejam31
<font color=red>First Rig:</font color=red> <A HREF="http://www.anandtech.com/mysystemrig.html?rigid=17935" target="_new"><font color=green>Toejam31's Devastating Dalek Destroyer</font color=green></A>
<font color=red>Second Rig:</font color=red> <A HREF="http://www.anandtech.com/mysystemrig.html?rigid=15942" target="_new"><font color=green>Toey's Dynamite DDR Duron</font color=green></A>
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