Windows 7: Help with a strange problem, Computer running super slow

Ok guys first time here so thanks for reading.

Ok here goes my problem, first off my power supply went out. It was a 450watt one I ordered and replaced it with a 750watt power supply.

After i replaced the power supply, my computer would not boot, When the power supply went out it was in the middle of updating windows. So I formated the hard drive and did a clean install of windows, reloaded all my drivers and extra programs. At that point my computer was running great.

I decieded to uninstall Bing tool bar, and windows live sign in assisant. it prompted my to reboot. When i rebooted the computer, after about 30 minutes it still hads not come up to the desktop, I could boot up in safe mode and it would run fine. I did a system restore, no change, I did a start up repair, no change, Tested the memory it came back fine.

So i got mad at that point and reformated the hard drive again, I had another hard drive formated it and put the install CD in and after 8 hours it is still trying to install Windows 7, No errors just really really slow.

So at this point, i have replaced the power supply, hard drive, and ran a memory test with no errors, done a clean install of windows.

Running Windows 7 64 bit, 4 gig of Ram, 2.8 dual core processor, 1 gig video card, 500 gig hard drive.

Any help would be great. I am leaning towards the ram being bad.

Don't rule out a motherboard (or CPU) problem. Since the power supply died while running, anything is possible. If you suspect memory, remove all but one memory module and see if that makes a difference.

Also, reset the BIOS and see if that makes any difference.

Ok tried removing a stick of the ram and booting, No change tried each stick seperate. I also went back and reset the Bios back to default.

My computer

CyberpowerPC GX1220 Desktop Gaming PC - Intel Core i5 750 2.66Ghz, 4GB DDR3, 500GB SATA II HDD, Nvidia GT 220, DVDRW, 420W PSU, Windows 7 Home Premium 64-bit

is there some kind of test to figuer out if mother board the issue?