Change button assignment by usb adaptor

[Gradius]

Hi. I'd like to know whether there is any way I could change the button assignment of my usb adaptor under win98. It's a 'BOOM' PSX-PC USB adaptor, to which I have plugged a PSX Joystick. The buttons on the control panel are numbered from 1 to 9, but one of the buttons is not 10, but 12. I would need to change it to 10 because it seems I have problems with the new MAME control system and this kind of configuraton  (it resets de control config as soon as you assing any function to that button). I hope they fix this soon. Wth another adaptor I have, which has its own drivers (SmartJoy), the buttons are numbered differently, but they go from 1 to 10, and there's no problem at all with the new MAME. I wonder if this button could be changed by editing some file or windows registry. I'm investigating this right now, but no success yet.