Activation is a technology used by Microsoft to ensure that you are following the end-user license agreement (EULA). Activation makes sure that the software is installed on the number of computers allowable and minimizes piracy from copying and lending installation CD’s. Here are some questions about activation.

Can I install a Microsoft product that has already been activated?
Yes, but you have to uninstall the software from the original computer and wait at least 90 days from the last activation before activating again. If activation fails, you can try the activate by phone method. (OEM copies are NOT transferable).

Can I activate a Microsoft product on more than one computer?
That depends. You should read the EULA to determine how many computers that product can be installed and activated on. Windows 7 and some Microsoft Office editions offer a 3-user license which entitles you to install the software on up to 3 computers at a time. Some editions of Office allow you to install a second copy on a portable device, as long as you ae the primary user of that device.

What happens if Microsoft detects the same activated product key on two or more computers?
The software may “phone home” at times to make sure that the same product key isn’t actively being used on more than one computer or what the EULA/product key allows. If it does find a violation, the software may ask you to re-activate the software on both systems. At that point, you must decide which computer you wish to activate the software on.

Is Windows Genuine Advantage the same as activation?
No. Windows Genuine Advantage verifies that you are not using a counterfeit copy of Windows, although it can send activation status of Microsoft products verifying that the software isn’t actively being used on more than what the EULA/product key allows.