I think the answers are valid for your setup. I understood very well what your configuration was. But for independent installations it does not matter whether both disks are physically in the box or not. When I install, one disk is always disconnected (mobo wire pulled).
PS: the only disadvantage of OEM is that it has to stay with the system (mobo). And I would go with 32bit unless you have more than 4GBs of RAM.