That would not require you reactivate Windows. Simply use cloning software to mirror your current OS installation to the new drive. If for some reason you want to dump everything on the old drive and completely start over with a fresh install, if this is a full retail version of Windows, there is no limit to the number of times you can activate it. You may have to call Mircosoft and get a new activation number after a few times, and an explanation that is suitable to Microsoft that you are not installing on more than 1 system at a time. That is, if this is a retail version. If it is an OEM version, you are going to have problems if you try to do a new installation.
Windows can be activated any number of times, but your re-activation experience will vary based on the way you acquired Windows.
* If you acquired Windows via retail purchase (boxed product), you may activate via the Internet the first five times. Subsequent activations are allowed but must be completed via telephone.
* If you acquire Windows pre-installed on a computer, re-installation would not require additional activation steps unless significant hardware changes were made.
To activate Windows on this computer, do the following:
Open Windows Activation by clicking the Start button > click Computer > click Properties > click "Click here to activate Windows now". If you're prompted for an administrator password or confirmation, type the password or provide confirmation.
For more information on Activating Windows, please click the following link: