oem seagate 20gb xbox 360

ok im not a noob as a tech! just noob as I dont post for help :) I have a 360 phat that gave a e68 when hard drive is plugged in. I took the hard drive out and hooked to pc and ran seagate tests on it! It passed! I need to know how I can re-partition a seagate 20gb OEM drive with its original...