Since we know we can examine the drive with a LiveCD and NTPASSWD to look in the registry, all you need to know is WHERE?
WHERE? Read http://forum.sysinternals.com/exact-windows-version-in-registry-key_topic1902.html
A friend has a system that runs Vista that will not boot. He wants to create a repair disk from another computer but isn't sure if the patient is running 32-bit or 64-bit. Is there a way to tell without booting the system? We can attach the drive to another system to check.