There are allot of things that start when you start windows, that tax the pc. These things are not running in dos. It’s like saying a car that runs just fine @ 5mph go 70 mph just fine; well..... Not if the transmission only has first gear.

I do agree it's frustrating, and there may be ways to fix it, have you tried testing the psu and testing the board with known good ram? Both would be worth trying to make sure the problem is on the motherboard or in the CPU.