Lost CD ROM drive

The CD ROM drive has to all intents and purposes
disappeared from my system. It was the E drive because I
have two hard disks.
I brought this about by trying to use the 'map network
drive' facility and unthinkingly using E. It didn't work
and the CD ROM drive 'disappeared' from the system.
I have tried to install a new drive and get asked for
drivers that I can't identify (the system is fairly old)
and anyway it seems to me that the drivers are still there
and a simple fix would be possible if only I knew what.
Any suggestions?