Problem in Windows 98 in Dos

Have a look at your DOS bootdisk files. You should have a config.sys and autoexec.bat file which can be edited with the DOS edit command.
Your config.sys file should look something like this:
device=himem.sys
device=emm386.exe NOEMS
dos=high,UMB
files=30
buffers=20

The himem.sys and emm386.exe files must be located on your bootdisk (in the root).
The files and buffers commands depends on the program you're trying to run.
The NOEMS parameter indicates that you require no expanded memory.
Theseare the basic parameters and should hep resolving your problem. Ensure that you have enough physical memory to run the software!
Good luck!

If you are trying to run this in a DOS window try this.
open windows explorer and find the executable Dos file. Right click on it and chose properties. You can adjust your extended memory under the Memory tab.