Stupid question but i have to ask are you trying to read a DVD rom data disk in a regular CDROM drive. Reason i ask is my cousin had the same problem couple months ago with an old P4 dell and back then when the P4s were new DVD ROM drives were not standard like they are now and she was trying to load a game that was a PC DVD and of course it simply will not read the disk and act like there is no disk there at all.

If it shows up in explorer like he said of course its enabled it would not show at all if the drive was disabled.