Junie-

you should be able to remove what you installed - esp if you know what program it was or the date you installed it.

go to settings- control panel - add or remove programs - double click it

a list will come up - you can sort if needed upper right

find the troublesome program and remove it.

or you could use the system restore and restore it to the date /time before the Cdrom disappeared.
Just follow the directions it gives you as you go thru the steps.