I was also having installation problems with this device at first, but I discovered that, under WinXP, if you plug the adapter into the USB port first, then plug in the joystick, it will report 'USB device not recognized', etc.  and appear as 'Unknown' under USB controllers in Device Manager.  Attempting to add the sidewinder through the gameport control panel also fails in that state; however, if you first mate the adapter to the joystick DB-15, then plug it into the USB port, it will recognize it properly and, under Device Manager, it will be listed as a Human Interface Device.  In my case, I have a Sidewinder Precision Pro and it identified it immediately.