Here is a solution for those of you who had no problems syncing your WinMo (Windows Mobile)smartphone with ActiveSync but have experienced problems when you switched to a WIN7 PC.
The Windows ActiveSync & WMDC Forum was of little help to me. I developed my workaround during a lengthy back & forth discussion with Tech Service Reps at my carrier. I hope this works for you:
1) Perform a Hard Reset on your SmartPhone. NOTE: This will delete your synced data on your SmartPhone. Don't do this if your WIN7 PC does not have your Outlook data.
2) Uninstall WMDC, WMDC Drivers etc from your WIN7 PC. Restart your PC to make certain your registry is updated (old habit).
3) Find out what version of WinMo/WMDC works on your SmartPhone (mine was a year old and used WinMo/WMDC v6.1).
4) Google-TM "WMDC (your SmartPhone version)", e.g. I used "WMDC 6.1".
5) Look for the MS/Windows URL to download the correct version of WMDC for your SmartPhone.
6) Download and install the correct version of WMDC for your SmartPhone. Restart your PC to update your registry (old habit).
7) Connect your SmartPhone to your PC via USB cable.
Go through the screens necessary for your connection and confirm what you want synced.
9) The first sync will be long since you used a Hard Reset to delete your old synced data.
This worked for me and I hope it helps some of you frustrated WinMo sufferers as well