This article describes how to increase the amount of conventional memory
available for MS-DOS-based programs in Windows. The following topics
- Determining current memory conditions.
- Making more conventional memory available.
MS-DOS-based programs require a certain amount of conventional memory to
run, even when you run them in Windows. If you attempt to run an
MS-DOS-based program that requires more conventional memory than is
currently available on your computer, the program may not run correctly
or at all, and an error message indicating that there is insufficient
memory to run the program may be displayed. When this occurs, you must
reconfigure your computer so that more conventional memory is available.
Determining Current Memory Conditions
To determine how much conventional memory is currently available for
MS-DOS-based programs, type the following command at a command prompt,
press ENTER, and then view the value on the Largest Executable Program
If the value on the Largest Executable Program Size line is smaller than
the amount of conventional memory required by the MS-DOS-based program you
are trying to run, the program may not run correctly or at all until you
reconfigure your computer. To determine how much conventional memory a
particular MS-DOS-based program requires, consult the documentation
included with the program, or contact the program's manufacturer.
Making More Conventional Memory Available
Device drivers and memory-resident programs that load from the Config.sys
and Autoexec.bat files can reduce the amount of conventional memory
available for MS-DOS-based programs. Increasing the amount of conventional
memory that is available for MS-DOS-based programs typically involves
removing unnecessary drivers and programs from the Config.sys or
Autoexec.bat files, replacing real-mode drivers in the Config.sys file
with protected-mode versions, or loading drivers and programs into upper
memory instead of conventional memory.
Removing Unnecessary Drivers and Programs:
To determine if a particular driver or memory-resident program in the
Config.sys or Autoexec.bat file is required for your computer to function
properly, consult the documentation included with the program or device
that installed the driver or memory-resident program, or contact the
program or device's manufacturer.
If you are not sure which program or device installed a particular driver
or memory-resident program, you can attempt to determine if the driver or
program is necessary by temporarily disabling the corresponding line in
the Config.sys or Autoexec.bat file. If your computer, the devices
installed on your computer, and the programs you run on your computer
all seem to function properly after you disable a line, the driver or
memory-resident program may not be necessary.
: Before you modify the Config.sys or Autoexec.bat files, you should make backup copies of the files. Do not remove any hard disk drivers, disk partitioning drivers, or disk compression drivers while you are attempting to determine if the drivers and programs in your Config.sys or Autoexec.bat files are necessary. For information about specific drivers
that should not be removed, please see chapter 35 of the Microsoft Windows
95 Resource Kit.
Replacing Real-Mode Drivers with Protected-Mode Versions:
Windows includes protected-mode drivers for many devices. In addition,
many hardware manufacturers provide protected-mode drivers for their
devices. To attempt to install a Windows protected-mode driver for a
device installed on your computer, follow these steps:
- In Control Panel, double-click Add New Hardware.
- Click Next, verify that Yes (Recommended) is selected, click Next, and then click Next again.
If the Add New Hardware Wizard does not detect the device and install a
protected-mode driver for it, you can attempt to install a Windows
protected-mode driver for the device manually. To do so, follow these
- In Control Panel, double-click Add New Hardware.
- Click Next, click No, and then click Next.
- Click the type of device for which you are attempting to install a protected-mode driver in the Hardware Types box, and then click Next.
- Click the manufacturer of the device in the Manufacturers box. If the specific device appears in the Models box, click the device, and then click OK to install the protected-mode driver. If the manufacturer of the device does not appear in the Manufacturers box, or the specific device does not appear in the Models box, Windows does not include a protected-mode driver for the device.
To determine if the hardware's manufacturer provides a protected-mode
driver for the device, contact the device's manufacturer.
Loading Drivers and Programs into Upper Memory:
To attempt to load one or more drivers or memory resident programs from
the Config.sys or Autoexec.bat files into upper memory, make sure that the
Config.sys file contains lines similar to the following lines (in the
Then, try loading device drivers in the Config.sys file using the
DEVICEHIGH command instead of the DEVICE command. In addition, try
loading memory-resident programs in the Autoexec.bat file using the
NOTE: If your computer is configured so that expanded memory is available
and you are loading the Mscdex.exe file from the Autoexec.bat file, you
can attempt to load part of the Mscdex.exe file into expanded memory using
the /E switch on the Mscdex.exe command line.
For additional information about increasing the amount of conventional
memory that is available for MS-DOS-based programs in Windows, please
see the following articles in the Microsoft Knowledge Base:
TITLE : A General Tutorial on the Various Forms of Memory
TITLE : Optimizing Your Use of Upper Memory Blocks
TITLE : Command-Line Switches for MSCDEX.EXE