1. If your system is rated for the processor then you should NEVER need to adjust settings (i.e. voltage).
2. At a glance, it is pretty obvious you have a memory error issue (Duhhh

) This is generally caused by 1 of 3 things....
2a. A bug in the offending program.
2b. A bug/glitch in the program vs. video driver or similar problem. In other words they fight over the memory location.
2c. A problem with the memory or its slot. This can be everything from failing memory stick, faulty slot, motherboard bios update needed, motherboard can't support the exact memory installed (i.e. single side vs double side), etc.
You replaced the power supply. A decent start. Might not have been necessary tho.
Either way....I'm assuming you replaced it with a brand name like Antec, Enermax, etc. Hint, if the power supply cost less than a cd-rw drive or a brand name motherboard it is junk. For a 500Watt supply I would expect to pay at LEAST 120 Canadian or about 85 USD. High quality supply's add 30-100% to cost I list (at the 500W range).
Next, use/make a boot CD to run MemTest86 or similar memory testing program. If you run into ANY errors, then try swapping sticks around or replacing them.
Next, LOOK at your motherboard, do you see fried capacitors (black), how about ones that are bulging or have some kind of orange/brown dust on top of them (kinda like a leaking battery). These are signs you need a new motherboard.
If you find no obvious problems from the information above, try using driver cleaner and installing a different video driver. I try to stick with either the ATI or Omega drivers. Remember to update your chipset drivers, etc before updating.
In my case I found memory errors. Tested the ram it failed. Looked at motherboard and found out capacitors were dying. Had to replace motherboard.
Good Luck