Joystick mapping button problem

I bought a generic usb joystick yesterday. After connecting to my pc, I went to the comtrol panel game controller settings and pressed each button to test whether it works. All the buttons are mapped correctly except for the 5,6,7 and 8 buttons. When pressing the LB (5), the 7 lights up and when pressing LT (7), the 5 lights up. Same with the RT and RB. The bumper and trigger buttons are reversed. How can I fix this? Is there any program that can map the buttons or is there a registry hack??