Take another look in those rc.d dirs. See if you can see something called xdm (or maybe it'll be kdm, or wdm etc... some sort of gui display manager).
If it's there that will be the thing starting X and showing the login screen.
A possiblilty worth considering is that maybe the change you made was to the default run level. Ring any bells?
Actually now I think of it, you said it was a fancy login screen. Probably not xdm then