Have you "fiddled" with the IDE plugs? With power off (better to be safe) re-position the plugs at the back of the PC. Are you "brave" enough to swap the hard drive and CD cables, to see if the fault "shifts"?
What do the device settings say?
Double Click the "My computer" on the desktop
Double Click the "Control Panel"
Double click the "System" icon
Click on the "Device Manager" tab on the top of the screen, the System Properties window will be displayed
If there are any problems with the drive a Yellow Exclamation point will be shown in front of the "+CD ROM" entry on the device manager window.
Click on the + sign in front of the "+CD ROM". This will open the CD-ROM section and show you the drive name that windows has detected. Click on the name so it is highlighted (blue) and press the properties button on the bottom of the screen. The CD ROM properties window will be displayed. There are at a minimum 2 tabs on the top of the screen. The General and the Settings.
When the General tab is pressed the "Device status" will be shown in the middle of the screen. This should normally say "This device is working properly".
When the Settings tab is pressed, you will see specific information for that drive. The assigned drive number is located here.
Good luck!