Problems with Vista Booting

I turned on my PC one morning to find that it kept sticking at the green loading bar screen in Windows Vista. I tried restarting it multiple times with no fix and eventually I let it sit at the screen for a while. Eventually it passed the loading bar screen and made it to the login screen. I was able to enter my login information for Windows without a problem, but upon trying to load the desktop, it took a really long time for all the startup programs to load. Once the dekstop was fully loaded, I tried to open a program. Instead of opening the program quickly, I got the Vista loading "circle" (like the hourglass in XP) and it took a long time for the program to load. Some programs such as Ventrilo would not load but instead just sit at the loading circle.

If I hit the start button, it would take a really long time just to bring up the Start Menu and whenever I tried to shut down the computer, it would just sit at the "Windows is Shutting Down" screen until I had to hit the power button the computer. I ran the Ultimate Boot Disc and ran the Hard Drive diagnostic for my HDD (WD Raptor 150). It reported no errors in the HDD. I decided to try to reformat Windows, but upon using my Windows Installation CD to reformat, it would just load a blue screen (not the BSOD, the blue screen shown when you are installing windows), but there would be no text or information boxes on the screen, just the mouse pointer with the installation background.

I ran the Ultimate Boot Disc once more and did a HDD wipe with the Active@ Killdisk program which successfully wiped my HDD. I then inserted my Windows Installation Disc again and was able to get Windows installed. After the fresh install, I was able to get to my Desktop with no problems and decided to finish installing my programs the next day. This morning I ran the computer only to have the green loading bar screen process normally, only to go to a black screen with no cursor or anything. This wasn't a display problem as my monitor was able to find the signal. I just don't understand why I was able to get to the desktop just last night, but now it stops at this screen.

I am now running MemTest86 to see if it's a Memory Issue and I'm starting to run out of options. Any help would be greatly appreciated. Here is a list of my PC parts:

E6750
Asus P5K Deluxe
EVGA 8800GTX 768mb
2x1GB Corsair XMS DDR2 800 PC2 6400
Western Digital Raptor 150 - OS Drive
Seagate Barracuda ST3400620AS 400GB - Storage Drive
OCZ 600W GameXStream
Vista 32-bit Home Premium