|Newegg has the same PSU for about $35. I bet you paid close to twice that much at Bestbuy.|
The optimal CPU:DRAM ratios for a Pentium Dual/Core 2 system are either 1:1 or 1:2. To arrive at the ratio, you should reduce the bogus QDR & DDR ratings to their actual frequencies. 800MHz FSB = 200MHz frequency, DDR 1066MHz = 533MHz frequency, so your current ratio is 200:533 which is 3:8. With your hardware configuration, you should shoot for 1:2, so you should either underclock the RAM to 800MHz or overclock the CPU to 1066MHz. If it were my system, I'd overclock the CPU.
As for your reboot loop, are you sure the heatsink was installed correctly? Did you use thermal paste or was a thermal pad pre-installed? If you used paste, it's very important to apply it correctly. And the heatsink must be securely attached, otherwise the CPU will overheat.
The Pentium Dual uses the "horizontal line" method:
The problem with your board/BIOS is the "memory multiplier" setting. With your 800MHz FSB CPU, you need a multiplier of 2.0. Is that even an option?