Can I do a clean install of Windows 8 - 64 bit on a brand spanking new 2 TB seagate barracuda? Would I be able to copy or run Steam games and Diablo 3 from my older hard drives?
Yes, you can can have separate drives for the OS and Steam. Lots of folks have a dedicated Steam SSD (drive). Windows 8 isn't ready for prime time quite yet for gaming. I would probably recommend the latest BIOS (UEFI) to 'hopefully' get all of the Windows 8 GUI to work properly.