Can you re-install Vista without Re-Registering it?

I am looking to find a way to re-install Vista without have to re-activate the license online or over the phone. I actually bought a license of ACRONIS TRUE IMAGE 11 HOME.. I made a bootable extact clone of already registered vista install from the current hard drive to a spare one with that software. I pulled old the original hard drive and booted from the newly cloned one and it worked perfectly except its asking me to re-register the vista online or over the phone. I mean it must have seen that it was different hard drive or something. So if there is anyone out there that has any idea how put a full exact backup of a already registed vista install onto a backup drive that you can have handy incase your current drive dies or gets gunked up with viruses and malware that you can restore from but NOT HAVE TO RE-REGISTER after you get it up and running Id be very appreciative. The main reason I want to not have to re-register is because this is for a person who keeps having me reload there vista install because the grand kids keep downloading spyware... it wont let me re-register without a hassle everytime now...please help!