I am sorry but have you tried the default built-in driver and does it fail to see the keyboard? iPaq wireless | Bluetooth connections | New | scroll way down to the bottom of the list, you should see connect to a keyboard.
Have you actually tried that?
And having said the above have you tried running
Think Outside Bluetooth drive on your PC to install it? The driver installed on my iPaq 210 when I was playing with my Bluetooth mouse. You do need to disable the built-in driver and this will require a few soft resets, but it does work...