As many of you are aware windows 10 Preview will have to be removed (on some systems) and the original OS re-installed to get the Upgrade License Activation..
Since you already have the preview of 10 installed - most likely you also have the drivers and windows driver updates installed..
If you export the current drivers from the windows 10 OS before you remove it - you can save the updated drivers to a folder - to be imported later into your New Windows 10 upgrade OS..
I am sure some will find a way clean install windows 10 and it is nice to have all the updated windows 10 drivers on hand and in a folder..
Create a "Drivers" folder on your drive (example> D:\Drivers) then run this command from prompt(admin) to export the current drivers
Once you install or re-install windows 10 - run this command to import the exported drivers into your new windows 10 OS
Dism /online /Export-Driver /Destination:D:\Drivers
Dism /online /Add-Driver /Driver:D:\Drivers /Recurse