You sure your CD drive hasn't been re-assigned another drive letter?
Alright. First thing I'd do is open your PC and check to make sure the IDE cable and molex power cable are both securely connected to the drive.
Secondly, I'd check in your BIOS to see if the device is listed and enabled.
Also, it might be a good idea to check your device manager to see whether the CD drive is listed there, and if so, what the status of the device is, and if not, then check to see if there are any unknown hardware devices with a yellow question mark.
|Desktop PC| |Macbook Air 13" (Mid 2013)|
|Windows 8.1 Pro (x64)| |AMD FX 4100 Black Edition 3.6 GHz @ 4.0 GHz OC| |Arctic Cooling Freezer 13 PRO| |Gigabyte Nvidia GeForce GTX 560 Super Overclock 1GB| |ASUS M5A78L-M/USB3 Motherboard| |Samsung 840 Pro 256GB SSD SATA III HDD| |Kingston HyperX 8GB PC3-14900 DDR3-1866| |OCZ ModXStream Pro 700W Modular PSU| |NZXT Vulcan Micro ATX Case|