HP has just released an update for iPAQ hx2000/hx4700 Series running Windows Mobile 2003 which enables the Pause and Next/Previous Track buttons to work properly with Microsoft Media Player 10. It's recommended to download and install the update if you are using a BT headset.

The update requires:
* Microsoft ActiveSync 3.7 (or later) is required.
* One of the listed iPAQ handheld models with ROM version 1.01 installed.

HOW TO USE:
1. Download the SoftPaq .EXE file to a directory on your hard drive.
2. Establish an Activesync connection between the handheld and host PC.
3. Execute the downloaded file. When the installation is complete, the handheld performs a soft reset.

Supported Models:
HP iPAQ hx2700 Pocket PC Series
HP iPAQ hx2400 Pocket PC Series
HP iPAQ hx4700 Pocket PC Series
HP iPAQ hx2100 Pocket PC Series

more info and download here