First, be absolutely sure you are used the FSDT installer, because an Cloud9 installer you might have, doesn't work on newer OS like Vista or Win7.
If you are sure you used that one, check you don't have an old version of the Esellerate engine in the system. Look for this file:
esellerateengine.dll
There should be only one copy in your system, and should be placed in C:\ProgramData\Esellerate if you run Vista or Win7, or C:\Windows if you run XP.
If you have another copy in the FS9 root folder, or a copy in C:\Windows but you are running Vista or Win7, remove all the duplicates.
Also, be sure your used account has admin rights. If not, run FS9 "As Administrator" when activating.