This isnt a usb adapter but the DIY parralel ps2 one...
Drivers psxpad
Psxpad web (i think some comercial ones use these also)
OS: XP
controller ids are "Psx Gamepad 1" and "Psx Gamepad 2"
buttons set if looking at a real psx pad are
PSX | NES
X | B
O | A
Square | Turbo B
Triangle | Turbo A
start and select are themselves
also this is in analog mode in digital those would be the digital pad not the stick if set in options otherwise
Dpad Left = Joypad 13
Dpad Right = Joypad 15
Dpad Up = Joypad 12
Dpad Down = Joypad 14
acording to your code atleast the drivers and other apps all start at 1 with the enum
these are default driver settings also figured id mention it since you can remap the button numbers to other buttons
ie you can make button 1 = X instead of triangle(default)