kool, ok first i want to make sure you have the right stuff, youll need:
soldering iron
solder
wire strippers
memory card
official microsoft controller this will not work with third party
usb cord
wire
what you need to do, crack open the memory card and locate the male part of the jack, u want to leave just that and the part of the board its attached to. no other circuitry. then solder each wire to a pin on the board. make sure you remember which wire you put where. i usually go from right to left red,white,green,black.
then make a hole at the top of the memory card for the wire to come out of. after that, crack open th controller, follow the cord until you find where its connected on the board, flip it over and solder a length of wire from each of the needed pins. you will need red, green, white, black, there should be two left over, yellow and blue/thick black, leave em, after that pick a port, youre going to kill it, take whatever means you use to cut wire and cut the port from the main board, leaving enough to solder onto, solder the wires that you spliced with the main wire to the corresponding pins, remember that this hasta match up with the usb cord you have running thru the memory card. after that youre pretty much done. all thats left is to install the drivers on you computer and plug and play. i havent found any drivers for linux or mac os x but for windows i use XBCD [XBox Controller Drivers].
google it.
there you have it, a removable usb cord attachment that doesnt require you to murder and hack apart a break away cable.
REMEMBER: DOES NOT WORK WITH THIRD PARTY CONTROLLERS.
i am not responsible if you screw up your controller of computer btw, just throwing that in there