Install on one disc, When you get to the welcome screen to enter a user name, hit ctrl, shift, F3 it will reboot in admin mode. Install all software and drivers. Run sysprep and it will be ready to clone to another drive for a different pc. It will take you through the oobe and you can manually enter the product key.
It would have been smarter to buy a technet subscription, and you would of had lots of keys for $349, you woulda had office keys also. And with 3 keys you could have activated all 25 of your computers. Each key is good for 10 activations, and you get 10 keys for all versions of M$ software. You would have had 100 activations for each version of windows or office for way less money.