I had the same problem..I had to get the USB adaptor...However..once I got that...i noticed that my joys would stick once in awhile in fast games..(Galaga and such)....not good..
So I went to X-Gaming and wrote customer service....they came back and said that there is a new USB device that addresses this issue and immediately shipped it out...with instructions on how to return my other USB adaptor..
I actually havent shipped it back yet

What they sent out was a Y-mouse...I just plugged the X-arcade into one of the y-mouse ports and plugged the port into the USB..plugged keyboard into X-Arcade,,,,,
BINGO.....everything works now