By default Windows uses all the memory it can get its hands on including the UMB. It is possible to force Windows not to use the UMB, so the DOS enviroment can be loaded in high memory and save conventional memory.

Select "Run..." in the Start Menu and run SYSEDIT.EXE. Select the file SYSTEM.INI, find the section [386enh] and write the following:

[386enh]
LocalLoadHigh = 1

Note this will only provide a benefit when running DOS games/programs within Windows.