The earliest WDYTYA versions of FTM were based on FTM 2005, later ones were based on FTM 2006, both versions will work with Vista but you need to download a patch to make the programme work.
Your version should be displayed in any family screen but If you want to check which version you have;
from the menu bar at the top of any family screen click "help", from the dropdown menu click on "system information". This will then display which version (2005, 2006 or V16) you are using.

The first topic on the FTM helpcentre (Family Tree Maker update for Windows Vista) gives an explanation and link for downloading the patch.
The helpcentre main page can be found via the following link
http://pastftm.custhelp.com/cgi-bin/pastftm.cfg/php/enduser/std_alp.php