If you are having problems synchronizing your HTC (WM6) phone with Vista using Activesync, here is a simple solution for you.
Activesync does not work with Vista and WMDC does not seem to help you. Well you can check the CD that came with your HTC phone (my reference cell is HTC Touch GSM). Install the WMDC drivers from the WMDC folder on the CD. After that restart your system.
Now plugin your HTC and follow the on screen instructions. It is very easy to setup synchronization this day rather than using 3rd party softwares.