Why don't you get one of these for less than 10 bucks and continue to use your Pronto but program it from newer computers?

[Link: microbarn.com]

After installation, you have to go to Device Manager and change the unit to use COM1 or COM2 (it deafults to COM21) in order for the ProntoEdit software to see it, but it works like a champ for me. Very fast data transfer.