Re: possible to move motherboard from 93450c to an older dri
to answer your question, no you cannot switch out ANY dvd drive for ANY replacement (even of the same make & model) it isn't just plug n play. Each xbox 360 dvd drive has a unique dvd key, this is what you need to extract from the busted drive and copy onto your replacement drive. Now to get the dvd key from the lite-on 7x and 9x series you are going to need to build or buy some hardware depending on which version lite-on drive you have.
Probably the best thing to do is have someone who is familiar with flashing xbox dvd drives to do it for you.
Also another recommendation is to get a hdd and install your games to it, this way the dvd drive isn't constantly in use while playing a game and should prolong its life.
my info regarding the xbox 360 dvd drives is based from experience, not sure if its 100% accurate & someone please correct me if im wrong, but I just tried to make my response short & sweet lol