It is stored in the C:/windows/system32/config. The hive you want is located under its name.
There is no "registry" on a motherboard. The Windows Registry is stored on the hard drive.
The registry is spread along different files but if I'm not mistaken the majority of it is stored in so called SAM.
The question makes no sense. The registry is where the keys are stored.
Registry
system.dat or restore.sys
Hkey_classes_roothkey_current_userhkey_current_confighkey_usershkey_local_machine
hives
system.dat or restore.sys
yes
system.dat or restore.sys
Hives
Hkey_users