There are inbuilt generic IrDA/Bluetooth modem drivers on the iPAQ. You don't need any Nokia software.
Just pair the phone and iPAQ in Bluetooth Manager and then if you go into Connections under Settings you can set up a dial up connection in there using "Bluetooth Dialup Modem". I recommend you set the baud rate to at least 57,600 if not 115,200 Kbps. This applies whether you are using GPRS or HSCSD.
You also need to go into dialling locations and then dialling rules and set them as follows:
Local number = G
Long distance number = FG
International number = EFG