It may not say anything about it in the manual, but there's no reason why your PC shouldn't accommodate one of those new fangled CD-ROM drives. Danny McAleer shows you where to poke your screwdriver...

Preventing your computer from looking like an octopus, with a plug in every orifice, and masses of trailing peripherals, is one of the distinct advantages of the new breed of all-in-one PC. But owners of more traditionally-configured PCs will still want to expand, and the peripheral of the moment is the CD-ROM drive. It isn't as difficult as you might think to fit one. The whole operation takes only half an hour at most, and is rendered simpler still by a full-colour installation guide from Silica Systems. But just before you hastily whip off the lid, be warned that in doing so, you are invalidating your warranty. Also, keep liquids, magnets, the pet gerbil, and any static devices away from the circuit boards.

Down to brass tacks

Because there are more types of PCs than there are excuses for not doing your homework, this guide is quite general, and it requires you to refer to your hardware manual on procedures such as removing the lid, and the internal layout. Despite a myriad of designs, all PCs have a plastic front panel with cut-outs on; the CD-ROM drive requires one of these 5.25" disk drive spaces. After popping this piece of plastic out, the drive mechanism slots into the runners, making sure that the front panel is level with the disk drive. Using the fixing screws supplied, the drive is then attached to the runners inside the PC.

The connections are just as straightforward. You must first locate a spare power supply plug, which will probably be minding its own business somewhere within the PC. It isn't hard to tell what cable is connected to the power supply, even among a rainforest of wiring (it's the one with a plastic opaque connector).

A ribbon connector and audio cable are usually supplied with the CD-ROM drive, as is a disk with the driver software. The ribbon connector is for the transferral of data to and from the PC and CD-ROM, and is fitted on the IDE board. Most PCs already have an IDE interface, although older and slower models like the 286 and under 20MHz 386sx will apparently experience some problems with some of the quad speed drives. But all is not lost if your computer is tortoise-like, because it is possible to obtain an additional secondary IDE interface card; indeed, some CD-ROM drives are actually supplied with one. The other alternative is to use the interface on a sound card, assuming it has an IDE and not a SCSI adaptor.

Making sure that the plugs on the end of the ribbon cables are properly lined up with the correct pins (pin 1 – indicated by a number on the board – corresponds to the coloured cable on the ribbon wire), connect the CD-ROM drive to any one of the IDE plugs. If a sound card has been fitted in the PC, you can connect the audio from the CD-ROM drive to the appropriate connections, to have the sound from the CD via the sound card's outputs.

Driving me mad

Like any peripheral with computers, you need some driver software that lets the machine know that something extra has been added. Some CD-ROM driver software comes complete with an executable installation program, which automatically makes any necessary adjustments to the autoexec.bat and config.sys files, whilst others depend on the user to edit the files themselves. It is advisable to make a back-up copy of each of these files before installing anything (although some programs do this automatically), and storing it away safely in a folder. Then, should you need to revert to your original settings, you don't have to go through the code, sifting out unwanted lines.

Manual installation may sound ominous, but is all rather simple if you know what to do. DOS and Windows already have an IDE CD-ROM driver included as an integral part of the package: MSCDEX.EXE. If all is well with your set up, this file will be found in the C:\DOS folder (if it isn't, there may be a copy of it on the CD-ROM disk, else you may need to re-install DOS). The line you need to add to the autoexec.bat file alerts the computer to run this program when it boots, and is written:

C:\DOS\MSCDEX.EXE /D:'device' [/E] [/K] [/S] [/V] [/M:n] [/L:drive letter]

/D:'device' (where device is the label given to the CD-ROM drive), tells the autoexec.bat file to start up the appropriate drive. After the device signature, there are four optional switches for expanded memory use, reading Kanji encoding, networking CD-ROM drives, and displaying memory statistics when starting MSCDEX.EXE. These aren't usually needed, and to avoid confusion, it is best to leave them out. The switch /M: is followed by a number; this specifies the number of sector buffers, and is also not strictly necessary.

However, the last switch, /L: is almost definitely needed. This specifies the physical drive letter for the CD-ROM drive. Some installation programs and SYS files automatically detect what the last letter in your system is. Usually, the CD-ROM drive is labelled 'D'. This is only the case if your hard disk has only one partition, and if there are no other external peripherals requiring a drive letter. This will be the letter you type in DOS prompt to access the CD-ROM drive.

The other file you need to edit is the config.sys; the line needed here is:

DEVICE=C:\CDROM\'name'.SYS /D:'device'

The folder doesn't necessarily have to be C:\CDROM; it can be anywhere, so long as the CD-ROM's *.SYS file is copied to it. For example, you could put it alongside the other *.SYS files in the DOS folder, to keep things tidy in the root directory. The 'name' is the actual file name of the *.SYS file provided with the CD-ROM drive. The /D: switch should be the same as it is written in the autoexec.bat folder.

And after all that, the CD-ROM drive should work, thus opening up a whole new world of multimedia-type software and games. Problems may occur with conflicting IRQ and DMA settings, with things like sound cards, but these can be easily rectified (see your sound card manual on how to do this). Also, if the software installation was manual, it is always best to double check and make sure everything is written in exactly, else you may find difficulties in getting the PC to recognise the existence of a CD-ROM drive. Also, remember to double-check all the connections inside the PC; if you're unsure, Silica Systems have an excellent technical support line for any of their products. Pester them for an answer, but bear in mind that you will need to provide them with as much information as possible before they can give you any answers.

And finally...

Although fitting a CD-ROM drive should be easy, there are some hidden swamps to tiptoe around, and chasms to bravely swing over with a frayed rope. You must ensure that unless there is already an IDE interface fitted to the PC (and you have a manual with at least the jumper configuration settings), that the CD-ROM drive is supplied with one. Either that, or you use the interface on the sound card.

Even here, there are things to look out for; IDE and SCSI are two completely different types of interfaces and whatever you try, one won't read the other. Also, some sound cards are fitted with drive manufacturer-specific interfaces, like Sony, Panasonic, or Mitsumi. The best way to do things, if you haven't already got a sound card, is to buy a complete 'multimedia' kit from Silica systems. This will ensure that everything gets along fine inside your PC, and you'll have many happy hours of CD-ROM driving.