Microsoft KB Archive/105071

= Microsoft Knowledge Base =

FastTips: MS-DOS 6.2 Configuration Questions and Answers
Last reviewed: November 23, 1994

Article ID: Q105071

The information in this article applies to:


 * Microsoft MS-DOS operating system versions 6.2, 6.22

1. Q. I receive the message "ERROR: Unable to control A20 line" during the startup (boot) process. How can I correct this problem?

A. The A20 line is a hardware component of 80286 and higher processors that allows programs to access the first 64 kilobytes (K) of extended memory. HIMEM.SYS must be able to control the A20 line to manage the extended memory on your computer. Since different computers use different techniques for controlling the A20 line, HIMEM.SYS cannot always determine the correct technique to use. If HIMEM.SYS cannot identify the correct technique for controlling the A20 line on your computer, you may need to use the /machine switch with the DEVICE=C:\DOS\HIMEM.SYS command in your CONFIG.SYS file. For further instructions, see your MS-DOS 6.2 printed documentation. You can also type "help himem.sys" (without the quotation marks) at the MS-DOS command prompt and press ENTER for information on HIMEM.SYS and the /machine switch.

2. Q. I made a change to my CONFIG.SYS or AUTOEXEC.BAT file and now my     computer stops responding (hangs) when I turn it on. What should I do?

A. MS-DOS 6.2 contains two functions that can help you correct this problem. The first function lets you bypass the CONFIG.SYS and AUTOEXEC.BAT files when booting. The second function lets you step through and confirm each startup command in your CONFIG.SYS and AUTOEXEC.BAT files.

To completely bypass the CONFIG.SYS and AUTOEXEC.BAT files, restart your computer and press and release the F5 key when you see the "Starting MS-DOS..." message. To step through CONFIG.SYS and AUTOEXEC.BAT, press and release the F8 key when you see the "Starting MS-DOS..." message.

NOTE: If you bypass your configuration files, some devices (such as the mouse) may not function. If you use a third-party disk-compression program, you should use the F8 key during startup and load any required device drivers. This is not necessary if you use Microsoft DoubleSpace.

3. Q. How do I add the Windows-based utilities after I install MS-DOS 6.2?

A. The MS-DOS 6.2 Upgrade includes Windows-based versions of     Microsoft Backup, Microsoft Anti-Virus, and Microsoft Undelete. To install these programs after you have installed MS-DOS 6.2, insert Setup Disk 1 in your floppy disk drive and run Setup with the /E switch. For example:

a:setup /e

If you are using MS-DOS 6.2 Step-Up, see the "Installing     Microsoft Backup, Undelete and Anti-Virus" section of the README.NOW file on your original MS-DOS 6.2 Step-Up disk.

4. Q. Now that I have upgraded to MS-DOS 6.2, my CD-ROM drive no     longer works correctly. Why is this occurring and how can I     correct the problem?

A. If MS-DOS 6.2 Setup finds the Microsoft Compact Disc Extensions (MSCDEX) in your AUTOEXEC.BAT file, it updates MSCDEX.EXE to     version 2.23. This version may be incompatible with your CD-ROM drive's device driver. Contact the manufacturer of your CD-ROM drive to determine whether your drive's device driver is     compatible with MSCDEX version 2.23.

If you didn't experience incompatibility problems with your earlier version of MS-DOS, you can avoid problems by replacing version 2.23 with your previous version. If you do so, you must also add the following command to your CONFIG.SYS file and then reboot your computer:

device=c:\dos\setver.exe

This problem may also be caused by a memory conflict involving MSCDEX. If you load MSCDEX in the upper memory area (UMA) and encounter CD-ROM problems, try loading it in conventional memory.

5. Q. Why do I receive the message "Out of memory" when I use the Microsoft Defragmenter, Microsoft Anti-Virus, or Microsoft Undelete?

A. The message "Out of memory" means that the program cannot access enough conventional memory. Use MemMaker to optimize your system and make more memory available.

If you are receiving insufficient memory error messages from Microsoft Undelete for Windows or Microsoft Anti-Virus for Windows, close a few Windows-based applications and try again. If the problem persists, exit Windows, restart Windows, and then run the application.

If you are receiving out of memory errors when you are running Microsoft Defragmenter, make sure you have at least 384K of extended memory available.

6. Q. After I compressed my drive, some of my MS-DOS-based games don't     work any more. What can I do to correct this situation?

A. Some MS-DOS-based games may not run correctly with the DoubleSpace component (DBLSPACE.BIN) loaded. Problems can occur due to lack of conventional memory, problems with application use of nonreadable video memory, or timing problems with sound files.

To work around this problem, install your MS-DOS-based games on     your uncompressed host drive and then start your computer without loading DBLSPACE.BIN by pressing CTRL+F5 or CTRL+F8 when the "Starting MS-DOS" prompt appears.

If you need specific CONFIG.SYS and AUTOEXEC.BAT files to run your games, put these files on the host drive for drive C. To     process these files, press CTRL+F8 when the "Starting MS-DOS" prompt appears and then press the ESC key.

To determine which drive is your host drive, type "dblspace     /list" (without the quotation marks) at the MS-DOS command prompt and then press ENTER.

NOTE: If you have MS-DOS 6.22, substitute DRVSPACE /LIST for the DBLSPACE /LIST command.