The Samsung Spinpoint F3 or Seagate Barracuda 7200.12 500GB drives both use a 500GB platter which helps them to be faster than 500GB WD drives, as well as quieter, produce less heat and due to the fewer moving parts mean that there are less parts to fail.
OCZ Ram is not really the best idea as they have reputation atm for having difficulties with mobos. Also you are unlikely to benefit from RAM faster than 1600mhz.
Win 7 64bit will utilize all the RAM in a system, which will include the VRAM on the graphics card. I've also heard there are security benefits over the 32bit version, altho I'm not clear about what these are.