Actually the power cable is fine. Its the PSU (power supply unit) thats crap. On variuous versions of the xbox the power supply unit had some crappy solder joints on the power supply near where the actual power cable plugs into the xbox. The joints crack over time/stress and the xbox shorts/sparks/smokes/catches on fire. What the replacement cord actually does is cut the power to the xbox if it sense this sort of power load/shortage. The power cable is fine, its the cheap PSU that is the problem.
Also, interestingly enough, when you order a replacement cable, if your Xbox has a "foxlink" brand PSU, you get a cable with all the fancy "anti" xbox starting on fire protection (its big and ugly). If your xbox had another brand PSU, you actually get an idneticle cable to what your currently have.
read more -> http://forums.xbox-scene.com/index.php?showtopic=361537