Oh, i just Cop'ed some thing..
When you Installed windows , Did you Still have 2 HDD's in the HP computer?
I Suggest , Install it on the HP with only the 1 HDD hooked up, This is Because if the Installer See's a copy of Windows on the Other HDD , it Will configure a Multi Boot, and Not A Standalone Boot, and that will case a problem, after you install it on the HP , Run The Sysprep Program as i said above , and this will Greatly improve the Chance of it working