An obvious thing when a drive doesn't recognize that a removeable medium is present is that the lens is dirty and it's unable to read the medium ID at the start of the disk.

A "cleaning disk" might help. If there's visible amount of fuzzies around the front end, just sticking a vacuum cleaner up close to the slot may pull some crud out.

You can also look in "Device Manager" - (assuming you're in Windows), and see if the device shows up, isn't marked as malfunctioning or a "don't use," and if a reasonable looking driver is hooked into it.

There are several ways to get into Device Manager, but in recent Win versions the easy one is in Windows Explorer, right click on "My Computer," pick Properties, click the Hardware tab, and there should be a button to open the Device Manager.

You'll see a branch called "Disk Drives," and you might find something interesting there, but the one you want in this case is more likely the "SCSI and RAID Controllers."

Assuming that you have the necessary installation disks, sometimes just deleting the driver and rebooting will let Windows find the device and install/reinstall the driver for it. In recent Win versions, you can expect Windows to have a usable driver for almost any drive of this kind, and it may find it on your hard drive or it may ask for your Windows installation CD. If it doesn't find one it likes, it should give you a chance to "Browse" to one you've downloaded.

John