Lost CD-Rom

Am running Windows 98. My system has lost the cd-rom. When it boots up it goes through everything ok, but all I can get it to show is floppy A and drive C. Cd-Rom had been D. Have tried to load drivers, reinstall windows, add hardware, device drivers, etc. etc. But cannot get it to show a CD-Rom. I seem to remember this is easy, but it has totally escaped me. TIA