cd driver missing in xp

I did repair reinstall of windows xp.  I had sp3, but disk was sp 2, so I ran updates, and reinstall of sp3.  when finished or maybe earlier, because I didn't check, the dvdrw drives were missing in xp.  They are seen in bios. but not in device manager, I did the upper filter, lower filter trick, with no help.  I don't know what is keeping windows from seeing the devices and loading the drivers.  I attached an external usb dvdrw and it works fine.  Any ideas

Thanks

Jon