Usually you can activate the same copy of windows about 3 times before you will be forced to call the activation line to do the process. However, if you're reinstalling on identical (or nearly identical; changing the hard drive should be fine) hardware, there's no point in wasting a reactivation, so it's good to be able to back it up directly. There are two ways you could do this.
If you want to do a full reinstall, it is possible to back up your activation files beforehand, and then restore them once the reinstall is done. I did this recently using these instructions, and it was super easy. To summarize (with some of my own rewording and clarification):
If using Windows 7 x64, also back up
You will need administrative
privileges to copy these files, and
may need to take ownership of the
files. If you need help with that,
comment below and I'll add details
about how to do that.
- Write down your product key. Since you have a retail installation, you
should already have it on the disk's
packaging. You can also use software
like SIW to extract it.
Once you have backed all of those up,
go ahead and reinstall. When prompted
to enter your product key during
install, leave it blank, and choose to
activate later. Once the install is
- Stop the software protection service by running
net stop sppsvc
in an elevated command prompt
- Restore each of the files you backed up before to their original
- Restart the software protection service by running
net start sppsvc
from an elevated command prompt
slmgr.vbs -ipk xxxxx-xxxxx-xxxxx-xxxxx-xxxxx from an
elevated command prompt, using your
key in place of the Xs
Finally, reboot. Your system should be
activated; you can check this by going
to System Properties from My Computer.
Windows Image Backup
The method which I would actually advise is to do a full image backup. If you have an external hard drive, then you can go to the Backup and Restore control panel and choose to "Create a system image". This will make a copy of everything on your system, which you can then restore onto the new hard drive using the recovery tools from the install disk. I've done this before as well, and it works great - when I had an hdd die, I put in a new one and had everything back to exactly how it was before right away when I restored the system image.