If you want to run and install *.umods in windows and it says unknown I've written a *.reg file to help associate the file type with unreal tournament. You will have to fix the location of your UT installation directory the one below is for steam users. Either copy in between the ==== and save as UT99umodfix.reg or do it manually

unreal umod file associations fix:
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REGEDIT4

[HKEY_CLASSES_ROOT\.umod]
@="Unreal.Module"

[HKEY_CLASSES_ROOT\Unreal.Module]
@="Unreal Module"

[HKEY_CLASSES_ROOT\Unreal.Module\DefaultIcon]
@="C:\Program Files\Steam\steamapps\common\Unreal Tournament\Help\Unreal.ico"

[HKEY_CLASSES_ROOT\Unreal.Module\Shell]
@="open"

[HKEY_CLASSES_ROOT\Unreal.Module\Shell\open]
@="&Install this Unreal module"

[HKEY_CLASSES_ROOT\Unreal.Module\Shell\open\command]
@="C:\Program Files\Steam\steamapps\common\Unreal Tournament\System\Setup.exe install \"%1\""
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