If you are using Windows Vista and have the Windows Mobile Device Center installed, you may want to download the latest version.  From the linked article, here are the updates in this version:

• Windows Mobile 6 feature support
  • Information Rights Management activation - Automatically configure the Windows Mobile 6 device to open IRM-protected documents and files
  • HTML mail – Set up your Windows Mobile 6 device to sync HTML-formatted mail
  • Certificate Enrollment - Acquire certificates through the PC the Windows Mobile 6 device is currently connected to
  • Allow data connections on the Windows Mobile 6 device when connected to the PC
  • File synchronization for smartphones – Synchronize files with your Windows Mobile 6 devices, including both touch screen and non-touch screen devices
• Automatic device authentication - Connect the Windows Mobile device to the PC without the need to enter the device-lock PIN every time upon connect
• Product Registration - Register your Windows Mobile device and get connected to information and offers available for your device