Windows 7 64bit Randomly Freezing - Upgraded From XP 32bit

I've recently upgraded to Windows 7 64bit, from XP 32bit, and since then have been experiancing completely random freezes, like, computer freezes completely, the last half a second of any sound playing repeats, and the PC requires reset, also, I've noticed sometimes when listening to music, the music will pause for only a second, then continue, which is strange. Now these freezes, and hangs, are completely random, I've had it happen 5 minutes after start up, and sometimes it wont happen for 3-4 days. I installed brand new ram along with the upgrade G-Skill F2-6400CL5-2GBNT DDR2 (2Gx2) in the correct DIMM slots Yellow and Yellow. Ran Memtest86+ for 10 hours, no problems and cleared CMOS.

Running Intel Core 2 Duo E6750 2.66GHz
4GB of ram
Gigabyte GA-P35-DS3L mother board
Gigabyte 9600 GT 512 MB

Bus speed 332.9 MHz
Rated FSB 1331.7 MHz
DRAM frequency 400.0MHz

Nvidia Geforece 9600GT
Core:600 Mhz
Shaders: 1500 Mhz
Memory:90 0Mhz