When you reinstalled the OS you changed the system information that activation uses to create a sig.bin activation file for that computer. Each sig.bin is unique to the user email address, the serial number, and specific OS information on that specific computer. If you simply go through the activation process again you should be all set. If you still have troubles you will need to contact support@stardock.com as we would have to verify all of your account information and that can't be done in this public setting.

Thanks for the reply. Btw I dont need activation right now. It was just a question regarding why the sig.bin wasnt recognize after a windows reinstallation.

So if I understand corretly, backup of sig.bin is mostly usefull if I uninstall the game. REinstalling windows need to generated a new sig.bin because my older one doesnt match?

Another benefit to keeping the sig.bin is that retaining the file if you have to uninstall the game and then reinstall it again on the same machine allows you to not have to activate it again. This causes your account threshold to stay the same. All software can be activated as many times as you need. However if they happen too rapidly then the activation gets maxed out and has to be reset by support. It is a security measure to prevent stolen account information to be distributed.