Help trouble shooting computer crashes

So I built my rig about year and half ago and ever since I've had random crashes that I've been unable to figure out. At first I thought its probably an incompatibility between the memory and the motherboard, so I ran memtest, twice finding no errors. I checked the error logs to find that I'm getting the error 41 kernel power or something like that and before that I had a critical error on ide port 4 which is what my cd rom and spare harddrive are hooked too. So I disconnected them considering I never use them and still It crashes.

Its crashed while I was on youtube, facebook, word, starcraft, seems like when ever it gets cranky it'll crash to the blue screen. All of my temps on speedfan hold around 45C except one that is always at a constant 81C which I think is reading incorrectly because in never fluctuates.

I'm running windows 7 on a
motherboard: gigabyte GA-770TA-UD3
CPU: AMD Phenom 955BE 3.2
PSU: Antec neo eco 520W
Memory: Corsair DDR3 2Gx2 XMS3
Video Card: XFX HD 4890
HDD: Samsung Spinpoint 500gig

Any guidanse will be much appreciated..... thanks also forgive me if I posted this in the wrong forum

actually I've noticed that I get quite a few

"The driver detected a controller error on \Device\Ide\IdePort4" errors

followed by"The driver \Driver\a1b0izof failed to load for the device ACPI\PNPA000\4&5d18f2df&0."

Then the critical kernal power error because it crashed to blue screen.....So maybe its a motherboard driver?