There is a program called Acronis true image 2010
Setup your OS with a fresh install of all the needed drivers, accounting / office software - and then make a disk image..
I use a 16GB USB stick which is bootable, to restore - boot from USB and restore image..
after you make a clean install image - add all your another juck software and make another differantial backup image..
Now you will have a clean install and a loaded install - now you can choose which one to restore..
Now you will never have to re-install, re-activate or re-register anything.. And I can now restore my fully loaded vista or win7 in 15 minutes..
The software sells for $49