Reserving a Letter for the CD-ROM Drive

Source: � 1997 Chin (can be freely distributed as long as I'm given credit)

To prevent the CD-ROM drive letter from changing when additional hard disc drives or partitions are added to a computer system, one needs to specify or reserve a specific drive letter for the CD-ROM drive. Use a drive letter other than drive D: and high enough in the alphabet to accommodate any additional drives that are added to or removed from the system. Reserving a specific drive letter for the CD-ROM drive is also a good idea if your computer system accesses a network. I usually use drive R: for the CD-ROM drive.

This procedure should be implemented before any software that will need to access the CD-ROM drive is installed. Naturally, this procedure can also be used after software has already been installed. Some programs, e.g. Microsoft Bookshelf, will prompt you to select a different drive to access the CD-ROM from. Other software may have to be reinstalled to get it to use the new drive letter for the CD-ROM drive.

Within the Windows 95/98 GUI

  1. Open Control Panel.
  2. Then double click on the System icon to load the System Properties utility.
  3. Click on the Device Manager tab.
  4. Click on the plus sign to the left of CDROM to display the list of CD-ROM drives.
  5. Click once on the CD-ROM drive that is listed. e.g. NEC CD-ROM DRIVE:222.
  6. Click on the Properties button.
  7. Click on the Settings tab.
  8. In the Reserved drive letters box, Change "Start drive letter:" to R: , "End drive letter:" should automatically change to R:. If it didn't, click on the arrow and select R: from the list.
  9. Click on the OK button to close the Properties windows and accept the new settings.
  10. Click on the OK button to close the System Properties utility window.
  11. Click on the Yes button to restart your computer to allow the new setting to take effect.

Note: If you do not need to access the CD-ROM drive from DOS, you can skip the following.
To insure that the same drive letter is used for both the "Command Mode" and within the GUI for Windows 95/98, the CD-ROM device driver and MSCDEX.EXE must be loaded when your computer is started. If you do not use any

From DOS / Command Mode

The CD-ROM device driver for your CD-ROM drive must be loaded from CONFIG.SYS.


Then the command,


has to be run before the GUI for Windows 95/98. You can put the command into AUTOEXEC.BAT or into a separate batch file that is called from AUTOEXEC.BAT.

I created a separate batch file named LD-CDEXT.BAT (Load CD-ROM Extensions) to load MSCDEX.EXE with the proper parameters to configure the OS to use R: for the CD-ROM drive. LD-CDEXT.BAT is called from the AUTOEXEC.BAT file using the command CALL LD-CDEXT.BAT. This is a safety measure to protect against the possibility of AUTOEXEC.BAT being modified or overwritten by an installation program and loosing the proper syntax for loading MSCDEX.EXE.

You should also include the command LASTDRIVE=R in your CONFIG.SYS file.

Now you can add or remove hard disc drives or change the number of partitions without having to worry about the drive letter for the CD-ROM drive changing.

For those programs that were already installed, you can use a program called Change of Address (CoA) to change the references to the old CD-ROM drive letter to the new drive letter that are in the Registry and .INI files.

In CoA, use the old drive letter followed by a colon as the old address, and use the new drive letter followed by a colon as the new address.

Review all the changes proposed by CoA. Make sure that there are no commands or words that end in "d:" that would be changed to an ending of "r:". This would cause the name of the command or word to change.

For example, one of the registry entries for Microsoft Graph is:        Default Chart=Standard:1,4.

COA2 (Change of Address) (coa2.zip): GetIt By Neil J. Rubenking
Change of Address lets you change the addresses of 32-bit Windows programs by changing the references to its path in the Registry and .INI files. Basically it does a search and replace. Publication Date: May 8, 2001 (v20n09) in PC Magazine.

Unfortunately, ZDNet/PCMag requires a subscription to download their "free" software. Alt.1

COA2 is actually the third version of this utility. The original COA was a 16-bit utility for Windows 3.1. The first update to COA, COA32, added support for the 32-bit Windows platforms that were available at the time: Windows 95, Windows NT 3.51, and Windows NT 4.0. Windows 3.51 has fallen out of usage, and some of the new Registry data types in Windows 98, Windows Me, and Windows 2000 caused COA32 to freeze up. That problem was the main impetus for this upgrade, but at the same time, we decided to streamline and enhance the user interface. http://www.pcmag.com/article2/0,4149,88432,00.asp

This tip was published in the December 16, 1997 (vol. 16 no. 22) issue of PC Magazine p. 293
You can check out Neil J. Rubenking's comments in Reserving a Letter for the CD-ROM Drive http://www.zdnet.com/pcmag/pctech/content/solutions/uu1622a.htm

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