On Windows there is this SID that identifies objects uniquely.
When you fresh install a Windows OS, it will generate a random SID that should uniquely identify it.
The problem is, if you clone that image and try to promote one as a domain controller and have the other one to join this domain, you will get to an issue where the windows gets confused about who is who.
To prevent this, there was sysinternals utility called newsid.exe which will generate a new SID and apply it so you don't have to reinstall the OS again.
But this utility is no longer being provided.
So then there is this sysprep tool which can generalize your OS so when you boot up next time it will generate a new SID.
If you bought your new laptop and upon powering it on the first time you would have experienced it asking for your username and things and setup for you.
Sysprep does just that so it actually takes up some time until it is setup.
Once you have setup the OS, applied required patches, installed some apps and ready to make it a template, perform the following.
1. Open explorer and navigate to "C:\Windows\system32\sysprep" folder.
2. Run sysprep.exe
3. Check "Generalize" box.
4. Select "Shutdown" from dropdown options.
5. After it completes processing, it will shutdown.
6. Take a snapshot
Now you can convert this to OVF or clone this when you need a new machine.