Then your Driver Installation failed.
In Vista, go to your System Settings to the Device Manager.
There you see a Yellow Button at a Device named "ADB".
Take a right-click with your Mouse and go to Driver Update.
Please search Manually your Driver files.
The normal Path to your Driver should be: C:/program files/HTC/Driver/Vista_X86/ (or so....)
Then your Driver get correctly installed and you will become a sync.
--> I really hope, that you understand my English. My English rusted since about 15 Years and I try now to do my best.