Thanks to -=CHE@TER=- (6-29-2026) for this info and the understanding of it.



The original issue is the patch/launcher (NWIV.COM) uses a filename that DOSBox can't use. This filename "$$$$NW4?.EXE" Where in the place of "?" there is a character with code 224 (0xE0) which is bigger than 126 (0x7E) - last allowed ANSI character in DOSBox. It seems that real DOS has less restrictions on filenames. Because of that DOSBox don't allow to create such file, thus the "NWIV.COM" would fail to work.

You can fix this by replacing 0xE0 with some allowed character (use any HEX editor you want):
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"NWIV.COM" fixes for an example:

Fix invalid temporary file name for DOSBox
NWIV.COM
0000591B: E0 70
00005928: E0 70
00005935: E0 70
00005A92: E0 70
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For example: 0000591B: E0 70 - it's an offset, old and new bytes in hex.



Fixed:
"NWIVa.COM" makes a proper build of "DUKE3D.EXE" which the tool then modifies and executes, when you quite it deletes the copied file: "$$$$NW4~.EXE".



