in the original "xecuter" kit there where 2 parts if i remember correctly, one was a adaptor to power the dvd drive, this was a white pcb (5cm long 2 wide) with a molex connector on it, two white push switches with leds to show use and a multi wire end going to a white connector that went into the 360 dvd drives proper power connector. this powers it as well as allows you to eject the drive and place the drive into modeb.
the other adaptor was for the 360 hdd and was also a pcb but was blue (8cm buy 1cm) with a molex but this also has a sata connector makde into the pcb so you could use it on the drive... this one is no good to you and may have damaged the drive if you used it. it looks long thin and has a slight notch on the end so it fits snug round the drive and only fits one way round.
this is it, the top is the one i described first, and the only one you should connect to the 360 dvd drive.http://www.xbox-modchips.com/xbox360-connectivity-kit.htm
the only usb part xecuter did was later i think and that was a blue plastic almost orb with 4 green leds in a plus shape on it, with a mini usb jack on one side and a sata connector on the other, this is just any old cheap usb to sata bridge, there is no power involved here, to use this you need the power kit i mentioned at the top.
this is the usb part you could use, personally i would get a cheaper one off egayhttp://www.xbox-modchips.com/x360-usb.htm