Dance Pad Code
Many recent PlayStation->USB adapters require you to enter a "Dance Pad Code". This code changes the mapping mode of the adapter to make the PlayStation D-Pad (Up, Down, Left, Right) to map to USB buttons so that opposite directions can be pressed simultaneously on the pad.
For most adapters, the code is:
Hold Up, Start, and Select for three seconds
The code can be entered at any time after plugging in the USB adapter to the PC. The code needs to be entered every time you restart your computer or plug your adapter into your computer. It is especially important that you enter the pad code before trying to map the buttons of the pad in StepMania.