Problem with Flight Simulator X

Hello,
My friend has been playing for months FSX on the computer (operating system Vista).
Recently, he remove the game and reinstall on the same computer.
Normally at the end of the installation than the screen with the demand for the activation code (registration) to be completed. The installation is successful, but the screen to activate appears not, so of course we can not register.
And calls made with Microsoft that gives us a number of tools has sent to all the rest of FSX files to remove and then reinstall to do. In vain.
The last board of Microsoft Windows reinstall. I think this is not a solution.
Has anyone same problems encountered with FSX ?

Remove the game even if this is not done yet.
Ccleaner to use your computer to scan all checked.
Then just check the registry, even with Ccleaner and restart the computer.

Then try installing again.
Download Ccleaner

The problem is solved. The last council was to Microsoft Vista in a new account to make FSX and reinstalling. New account, there through the shortcut on the desktop FSX started and the screen to register came out (I have FSX on the new account does not have to reinstall).

If this not succeed, then I had to re-install windows. Who knows. Microsoft has become corrupt my account, whatever that means.