I kept the hard drives from the previous build and everything was working fine until I upgraded everything this evening. Whenever I boot into Windows 7 x64 I get to the "Starting Windows" screen, the balls freeze, and I get a BSOD and immediately reboot. I also dual-boot with Linux Mint and can boot into that with no problem. I'm thinking it's a memory problem because the LEDs light up just before it reboots with the BSOD.
So you using the same hard drive you used from 2008 to the new computer? Windows operating system is hardware specific. You should read the following link and see if it works for you. If not you should do a fresh install of windows 7.