I just learned something interesting.
If you replace the motherboard of an eMachine and then try boot up, it won't work correctly. The OS in the machine is set up to work only with the motherboard provided by eMachines. The restore discs will not work with it either. If you replace the motherboard of the eMachine, you'll have to provide your own OEM OS.
I didn't know eMachines was that proprietary.