You can use a computer CD drive to play CDs WITHOUT A COMPUTER
It might seem a strange thing to suggest, but it's true. A computer CD drive can be used for playing CDs on its own without being part of a computer.
First, let's make one important thing very clear before going on about it: The CD drive MUST have TWO buttons on the front. Some CD drives have only one button, which presumably saves a penny in production. This type won't do - it has to be the TWO BUTTON variety for this trick!
However, the good news is that the CD drive doesn't need to be 128X speed or anything silly like that. The best ones for this are the old 2X speed or even single-speed drives.
So, having got that sorted out, the connections for the CD are: Power in (required), Audio out (recommended), and NO IDE DISC CABLE.
Audio out is the easy bit, as this consists of a piece of cable that would normally connect to the sound card. Lop this off and wire it up to one of the inputs of a hi-fi with the following wiring:
Red: Right
White: Left
Metal outer braid: Ground
Or to put it another way: Left channel = [white, ground] , Right channel = [red, ground]
Next, the power. This requires the cable of the type which would normally go into a hard disc drive, and one easy way to power a CD drive on its own is to use a computer power supply. Another way is to provide your own supply, considering that the power connector wiring to the CD drive is:
Red: 5 volts
Black: 0 volts
Black: 0 volts
Orange/Yellow: 12 volts
This can be achieved by using two 6v motorcycle batteries in series, with a diode to drop the centre-tap to 5.3 volts, which is most likely near enough. You can also use rechargeables, but don't use dry batteries as they are expensive and might not be able to supply the current.
Another helpful design note: Computer CD drives aren't especially vibration-proof and will only work the right way up, so if you are thinking about fitting a computer CD drive in your car dashboard, check it's going to work ok first by driving around a bit playing a CD with the drive on a tray on the passenger seat BEFORE cutting a hole in the console!