A molex to sata adapter won't work since the XBOX ODD has another type of connection. I've posted a link to a homebuild, but the only thing you need to do is connect 12v, 5V, 3.3V and GND to appropriate connector-pins and also a swith between GND and 3.3V and the open/close pin (pull it high or low).
Here's the link to my post:http://www.xboxhacker.net/index.php?topic=7649.0
If you have a SATA power connector (wide, black with a lot of pins) it also has these four needed wires, +5V usually red, +12V usually yellow, +3.3V usually orange and GND is usually black. Check before you connect.
Either cut an extra SATA power connector off and connect to the ends or open the plastic shield of the wires a bit or simply cut it off an inch or so from the connector (to be able to put that shrinking tube on it) and solder on wires at appropriate length for the 360's ODD.
That's what I plan to do anyway, then I might solder pins to a small board if I can't find a connector that fits the ODD 6x2 pin powercord (two empty positions). Details in the link above.