Found this when looking up your "hypothetical" situation...
So "if" this was you, could you just go into MS Dashboard, Settings, Time and set the clock, since you said it only does this sometimes when it randomly reboots? Otherwise, here is a more in-depth tutorial: http://forums.xbox-scene.com/index.php?act=ST&f=3&t=53268
If you do replace your DVD drive, the best is the Samsung, second best is Phillips, Thomson is the worst (this is the one I have ). (According to www.xbox-scene.com forums)