I put in a DVD rom instead of a regular 40x cdrom.

Ever since i changed the cdrom, xp sometimes starts differently.
Right after the bios, and right before the initial windows logo, i get this black screen with a horizontal bar at the bottom that shows progress or something like that. It's initally empy, and then very fast filles up. (sort of like a scandisk bar that shows % of scan completed"

What is that? And why is it showing up all the sudden like that?

Thanks

In Win2K or WinXP, that progress bar is normal.