If I go into my BIOS settings and change anything to do with the CPU, my computer will go into a boot cycle and won't go past POST. This happens to me even if I do something as simple as changing the Performance to the higher setting on the EZ menu.
If I reset the CMOS it will reset to default and I am good to go. However, am I trying to overclock.
The PSU is horrible, yes, and I definitely think you should replace it, but I'm not sure that's the problem.
I'm guessing your RAM configuration is 4x2 and 2x2? Try taking out the 2 2GB sticks to see what happens. Weird RAM configurations like that tend to cause problems sometimes, and the sets are obviously not matched, so that's a concern, as well.
Also, if it's 4x3, that's a strange configuration as well, and it wouldn't surprise me to see that cause a problem either.