The fact you are using a 64-bit OS has almost no impact on the installation. It does mean that, if you must install drivers, they MUST be for the 64-bit OS you are using.
Now, your post confuses me a little. There are no single-disk RAID drives. So, are you actually installing a pair of matched drives to be used in a RAID array? Or, are you adding a second drive to an existing machine and converting it from a single-drive machine to a RAID array system? If you are really only installing a single HDD it will not be used as a RAID unit, even though it may be rated for use in RAID systems.
Post back here exactly what you are doing, including what motherboard you are using, what hard drive(s) are already in the system (manufacturers and model numbers), and what new hard drive(s) you are adding. How are existing drives being used, and what system do you want to convert to?