EDIT: I just found the original site on the topic. You can view it here (http://www.tabletpcbuzz.com/forum/topic.asp?TOPIC_ID=16780). The instructions are pretty much identical to what I wrote, but I felt it was necessary to post it anyway. Enjoy.
It is actually quite simple to use the built-in Windows XP SP2 bluetooth drivers with the "Bluetooth by hp" card that you can get with these laptops. Just follow these instructions and you should be all set. The Windows XP drivers are not complete, but they are more than adequate for the average bluetooth task.
1. Remove the old bluetooth software using Add/Remove Programs.
2. Turn off the wireless button to disconnect bluetooth.
3. Open the file C:\WINDOWS\inf\bth.inf in Notepad and look for the following entry:
[HP.NT.5.1]
"HP USB BT Transceiver [1.2]"= BthUsb, USB\Vid_03F0&Pid_0C24
4. Directly after that, add the line:
Bluetooth by hp= BthUsb, USB\Vid_049F&Pid_0086
5. The whole entry should look like:
..
[GVC.NT.5.1]
GVC Bluetooth Wireless Adapter= BthUsb, USB\Vid_0525&Pid_a220
[HP.NT.5.1]
"HP USB BT Transceiver [1.2]"= BthUsb, USB\Vid_03F0&Pid_0C24
Bluetooth by hp= BthUsb, USB\Vid_049F&Pid_0086
[IBM.NT.5.1]
Bluetooth UltraPort Module from IBM= BthUsb, USB\Vid_04BF&Pid_0317
IBM Integrated Bluetooth= BthUsb, USB\Vid_04BF&Pid_0318
IBM Integrated Bluetooth II= BthUsb, USB\Vid_1668&Pid_0441
IBM Integrated Bluetooth III= BthUsb, USB\Vid_1668&Pid_2441
..
6. Save the file and close it.
7. Turn on the wireless again and the Bluetooth by hp device should be recognized and installed automatically.
8. You will now be able to use the Windows XP bluetooth drivers for your card.
If you have any problems with these instructions, please let me know as I am writing them from memory. I haven't installed it in a while, but I did take the quotes directly from my working file. I will make any updates as needed.