OK for the start get an xbox original controller or something similar like ps2 should work
get an usb cable like for a printer not a usb extender very important it can and will break your port.
Just cut the end of the usb cable that plugs into the device not the one that you plug into the computer off and strip the insulation back. Careful alot of cables Iv come across come with a thin wire mesh shielding (Sharp) cut that off and the insulation you stripped back off.
Repeat for the xbox controller wire
If your doing this with an original xbox controller you will see a yellow wire just cut that off its not needed
Once everything is stripped back peel the BLACK GREEN WHITE AND RED WIRES ON BOTH CORDS AND MATCH THEM UP ACCORDINGLY
BLACK<--->BLACK
WHITE<--->WHITE
GREEN<--->GREEN
RED<--->RED
I personally twisted each of the wires together and bound them with electrical tape each individually then once they were all bound wrap the entire thing in electrical tape
Or If you feel cool and have a soldering iron and solder just solder them together
Once that is finished and you feel comfortable with how secure your cable is Download http://www.filefront.com/15017275/XBCDv107.exe
Install this before plugging the controller in preferably may need to restart afterwords.
I don't have a computer with xp on it don't know if it will work.
Works great on vista and probably windows 7
once that's done download this
http://www.filefront.com/15017327/xpadder_gamepad_profiler.exe
then open new
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Hit enable for everything that has enable and follow its instructions
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When you get to Buttons tab push every button including both triggers and click the joysticks
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After this is all done hit finish and click one of the buttons on this screen test them out and see what does what on the controller
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I personally bound them to random junk I don't use much and I use a barmod in wow that I can bind keys to what I want just match them up to have whatever button on the controller do a spell Dont forget tab somewhere in there unless you want to use mouse clicks to find your target they can be bound as well
Push the wrench on whatever combination is Joysticks and bind one to wsad and the other to normal mouse movments (may need to ajust the sensitivity in game)
Save it when you get it all set up the way you want and your done got your self an xbox gamepad
P.S If you have a free button or just want to do this go Into a key thats free push advanced and Start a cycle Have it push one of your spell keys you click it Change the pause to the GCD or a little long to account for wow lag and do that for every spell you want in the sequance like this
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If you don't like the way I explained it don't complain just Google around its somewhere.