You have probably already done this stuff but here are tips from HTC's site.
Tips:
If you cannot see the HTC Sync option when you connect your phone to the computer via USB, please follow the
Instructions below:
1. Make sure you select USB Debugging in Settings > Applications > Development before connecting your phone to the computer
2. Connect you Phone to the PC and wait 20 seconds for your phone to install HTC Sync on your phone.
3. Unplug the USB sync cable. Wait for 5 seconds. Reconnect the Phone to the PC using the USB cable.
4. Select ?HTC sync? and wait for HTC Sync to recognize your Phone. This process could take up to a minute your first
time connecting to the computer.
