How to Create a Bootable CD-ROM

If you are not already aware of it, you can boot up your computer via a CD, as if it was a floppy disk or hard disk. To this end, the CD has to be bootable and you must change the computer's set up to allow booting via CD (the Boot Sequence option should be changed to something like CDROM, C).

We often have to make a bootable CD. The usual case when we must run an antivirus program on an infected computer. As the machine will be booted through a CD and seeing that data cannot be directly written on a CD, it is much more sensible to run the antivirus this way (the virus has no way of attacking the CD). Furthermore, current antivirus programs are too big to fit on a mere floppy disk.

To make a bootable CD, just chose, from the CD recording program, to create a boot CD. In Easy CD Creator, for instance, this is accomplished on the File menu, option New CD Layout, by choosing Bootable CD. The program will then prompt you for a floppy disk containing the boot's image.

Bootable CD-ROM

Figure 1: Making a Bootable CD with Easy CD Creator.

And what is this? Well, to be able to boot, the CD has to contain a file holding an image of a boot disk. This will allow it to boot by simulating the floppy disk. In other words, you will have to set up a boot disk in the precise way you want to boot via the CD.

During the boot, the computer will perform as if it was really being booted by a floppy disk. This virtual floppy disk (the image of the disk recorded on the CD) will be accessed as letter A of the operating system. The computer's floppy disk drive (drive A) will be accessed through letter B.

You must create a boot floppy disk that will also make the system recognise the CD-ROM drive, seeing that when booting via CD the computer believes that you are booting by using a normal floppy disk, not aware that you are booting via a CD. In other words, you must prepare a boot floppy disk that works precisely the way you wish to run your boot from CD.

We recommend that this boot floppy disk to be used as an image on the CD be created through the following commands on the DOS prompt of a machine running Windows 98:

Format a:/s
Copy c:windowscommandebdoakcdrom.sys a:
Copy c:windowscommandmscdex.exe a:

Then create a Config.sys file via command Edit a:config.sys containing the following command:

device=a:oakcdrom.sys /d:mscd001

Next create an Autoexec.bat file through command Edit a:autoexec.bat containing the following command:

a:mscdex.exe /d:mscd001

Your boot floppy disk is ready now and you can use it. If you want to automatically run a program – for instance, an antivirus – just add the command that calls up the program in the last line of the boot floppy's Autoexec.bat file. Note that after command Mscdex, the computer will already acknowledge the CD-ROM drive. For instance, if you have written the F-prot antivirus on a CD-ROM in a directory called F-prot, the last line of Autoexec.bat will then be:

d:f-protf-prot.exe

BTW, this antivirus can be downloaded at http://www.f-prot.com.

Note that we assume that the CD-ROM drive will be accessed as letter D. If you boot via CD a computer with more than a single hard disk or with a hard disk with more than one partition, a message path not found will appear. You will then have to run the command manually.