WMDC (Windows Mobile Device Centre), is the new software in Vista that replaces ActiveSync and you cannot even install ActiveSync on Vista.
If you installed Vista RC1 and plugged in your Windows Mobile Phone (either Pocket PC or Smart Phone) and expected Outlook to start syncing you would be in for a rude shock. All Vista does is open the device in Explorer so you can browse it and get to explore files - but nothing to sync up. This is because the WMDC bits are not publicly released yet but are being dogfood'ed internally.
If you are like me and cannot wait then below are the steps you need to do to get your mobile sync between the device and Outlook / Exchange using WMDC (make sure you also read warning before you do anything):
1. Add a new key called "WHOS" (without the quotes of course) in HKLM\Software\Microsoft. (See the image below on how this should look like with the blue circle around the key)
2. Plug in your mobile to the machine (either via USB or your Cradle).
3. Run Windows Update.
Windows Update should detect that you have a new update and download and install the WMDC bits. After which you can setup a new partnership to get this running with Outlook.
Previously posted at blog.Solidsoft.com