The Backup option is enabled when the product is active and you want to backup your key. It's not a "restore" key.
If you made a backup of your system (at least your own files...), the old backup key was saved in your "Home" folder, the one that contains Pictures, Videos, etc, which is usually located on C:\Users\YOURNAME so, if you have it, it's enough to double-click on the .REG file, confirm to insert they key in the registry, and on the next restart, the sim will ask you if you want to activate it, so you'll just have to confirm, and it will activate without manually typing the key.
If you haven't made a backup of your system, just select the "Register Serial" and type your key MANUALLY. Your key is of course in your purchase receipt.
If you have lost your purchase receipt, the FAQ page of this site explains how to retrieve it.
Of course, all of this was already explained:
- In the FSDT_install_guide.pdf, which comes with every product
- In the sticky thread named "
Reinstallation after system upgrade or crash, please READ!" in the General section.
http://www.fsdreamteam.com/forum/index.php/topic,649.0.html
