I have two spare computers, one running Windows 7, the Other XP and my maim machine running Windows 7.
This is not a networking question.
Is it possible to link one or two of the spares to my main machine to harness their processing power and memory to the benefit of the main machine? Possibly use the drives for storage and backup but all programmes and applications on the main machine.

I have two spare computers, one running Windows 7, the Other XP and my maim machine running Windows 7.
This is not a networking question.
Is it possible to link one or two of the spares to my main machine to harness their processing power and memory to the benefit of the main machine? Possibly use the drives for storage and backup but all programmes and applications on the main machine.

Yes you can. What you need to do is create a bonnet environment with your computers. Google bonnet and NASA because they created this environment to create one of the first super computers.