To operate in a DOS environment, a CD-ROM drive needs a device driver that is loaded from the CONFIG.SYS file. The driver interfaces with the drive and with a real-mode program called the Microsoft CD-ROM extension for DOS (MSCDEX.EXE), which must be loaded from AUTOEXE.BAT. Both of these programs will come on a floppy disk with the CD-ROM drive. Run the installation program that is also on the disk. It copies the files to the hard drive and edits both the CONFIG.SYS and the AUTOEXEC.BAT files. Restart the computer so that the changes will take effect. If there are problems accessing the drive after you have restarted, check the items listed under “Troubleshooting Guidelines”.
Install the Device Driver for Window 9x
Window 9x supports CD-ROM drives without add-on drivers. Click Start, Setting, Control Panel, and double-click Add New Hardware. Click Next when you are prompted, “To begin installing the software for your new device, click “Next”. Complete the installation by following the directions on the Add New Hardware sheet.
When Windows 9x starts up, it assigns the next available drive letter to the drive. To dictate what the drive letter should be, use Device Manager. Click Start, Settings, Control Panel, and select System. Click the Device Manager tab. Select the CD-ROM drive and click
Properties, then the Settings tab, where the drive is designated E: Select a range of letters to be used by the drive and click OK.
Test the Drive
The drive is now ready to use. Press the eject button to open the drive shelf, and place a CD in the drive. Since data on CDs is written only on the bottom, be careful to protect it. Now access the CD using Explorer (use the assigned drive letter).
If you have a problem reading the CD, verify that the CD is placed in the tray label-side-up and that the format is compatible with your drive. If one CD does not work, try another the first CD may be defective or scratched.
Update your Windows 95 Rescue Disk to Include Access to the CD-ROM Drive
The Windows 9x emergency startup disk you created in earlier chapters to start a system in the event of a hard drive failure need to include access to the CD-ROM drive because Window 9x is normally loaded from a CD-ROM. Windows 98 automatically adds the real-mode CD-ROM device drivers to this rescue disk, but Windows 95 does not. This section explains how to add this functionality to the rescue disk.
Windows 9x have its own built-in 32-bit protected-mode drives for CD-ROM drives, but when booting from a rescue disk, you will be using older 16-bit real-mode drivers. Two files are required, the 16-bit device driver provided by the manufacturer of the CD-ROM drive (or a generic real-mode driver that works with the drive) and the 16-bit real-mode OS interface to the driver, MSCDEX.EXE. The device driver is loaded from CONFIG.SYS and MSCDEX.EXE are loaded from AUTOEXEC.BAT.
If you have run the DOS installation program that came with the CD-ROM drive, then your AUTOEXEC.BAT and CONFIG.SYS files should already have the correct entries in them. You
can add these lines to these same files on your rescue disk, correcting paths to the two files as needed. Copy the two files to your rescue disk, and you should be able to access the CD-ROM drive when you boot from this disk, even when the hard drive is not accessible.
For example, on a rescue or boot disk designed to access the CD-ROM drive without depending on any files or commands on the hard drive, the CONFIG.SYS file might contain this command (the parameters in the command lines are explained below):
DEVICE = SLCD.SYS/D:MSC001
The AUTOEXEC.BAT file might contain this command line:
The explanations of these command lines are as follows:
Two files needed to manage the drive are MSCDEX.EXE and SLCD.SYS, which must be copied to this disk.
When the program MSCDEX.EXE executes, it uses the MSCD001 entry as a tag back to the CONFIG.SYS file to learn which device driver is being used to interface with the drive- in this case, SLCD.SYS.
To MSCDEX.EXE, the drive is named MSCD001 and is being managed by the driver SLCD.
MSCDEX.EXE will use SLCD as its “go-between” to access the drive.
MSCDEX.EXE also assigns a drive letter to the drive. If you want to specify a certain drive letter, use the /L: option in the command line. In our example, the CD-ROM drive will be drive E. If you don’t use the /L: option, then the next available drive letter is used.
The /M: option controls the number of memory buffers.
If the files referenced in these two commands are stored on the floppy disk in a different directory than the root directory, then include the path to the file in front of the filename.
If your hard drive fails and you start up from your rescue disk, once the CD-ROM drivers are loaded and the CD-ROM drive is recognized, you will be able to install or reinstall Windows 9x from CD. To do this, insert the Windows 9x Cd into the CD-ROM drive, and from the CD-ROM drive prompt (either D: E: or some other letter), type Setup, and then press Enter. Once Windows 9x is installed, it will often ignore existing CONFIG.SYS lines (turning them into comment lines by adding REM to the beginning of the line) and handle the CD-ROM drivers through its own protected-mode drivers.