The Expanded Memory Manager EMM386.EXE can be configured to allocate the memory beyond the 1 MByte according to the expanded memory specification (EMS) instead of the eXtended memory Specification (XMS). This is useful when running games and programs that requires expanded memory.

Edit CONFIG.SYS and update/insert these lines to emulate 1 Mbyte XMS as EMS:

DEVICE=C:\DOS\HIMEM.SYS
DEVICE=C:\DOS\EMM386.EXE 1024 RAM
DOS=HIGH,UMB

Note that the parameter "RAM" will of course not work together with the "NOEMS" parameter. When using the "RAM" parameter 64 KByte of the Upper Memory Block (UMB) will be taken.

More Info MS KB76916
More Info MS KB96759
More Info MS KB275423