PC Upgrade gone horrible

I like to upgrade my PC hardware every few years, keep things current. I did exactly that just a few days ago. I replaced the motherboard, processor, and RAM:

EVGA P67SLI Micro
Intel i5-2500 3.3GHz
12GB Mushkin DDR3 SDRAM DDR3 2000 (PC3 16000)

The harddrives and PSU (1000W) are the same and I was already running Windows 7 so that was current. I should say before I go on that I was having absolutely no issues whatsoever up to this point with my system.

Initially, I swap out the old hardware for the new and try to just go with it but when I tried to boot up Windows to could not get past the loader screen before it would blue screen and reboot (I've no idea what the blue screen said, it would stay up for a fraction of a second). After some browsing of the Microsoft forums I basically find out that Windows 7 doesn't handle swapping hardware very well and I needed to reinstall Windows. As much as I didn't want to, I did reinstall the OS with a clean partition. Windows now actually loads with no problems, but I'm facing a completely different problem. I have issues getting nearly everything to install properly (to give some examples, Microsoft Office took 3 attempts to install properly and completely, Starcraft 2 took 2 tries to install but all attempts to update fail and crash, I cannot install League of Legends). I encountered a number of different blue screens trying to reinstall all my programs as well. Given that Office and SC2 are installed from DVD but League of Legends and some other programs were installed from a downloaded file, my only conclusion left is that the hard drive is the issue? Does anyone else have any ideas or do I just need to replace my hard drive?

It probably said 0x0000007b.

If the hard disk was working fine before, I would presume that the issue is with the new components. Is Prime95 torture tests stable for several hours? What about memory? Did you run Memtest86 or Windows memory diagnostics for several hours?

You are right, it is 3x4GB sticks.

The RAM I had in my previous setup was Corsair Dominator DDR2 SDRAM DDR2 1066 (PC2 8500). It wont work with this board or I would have tried it.

I guess if you don't want to spend money, you can try taking out 2 sticks and see if stability improves.