wrong in our case we speak about Windows NT Non-Win16 application shell, Implementing DOS Support for Windows DLL’s located in:
c:%WINDIR%\system32\winoldap.mod

btw. mod was/is also audio file (amiga tracker format etc)

these Unreal Modification Package installer files you speak about are so called Umods

Unreal Tournament
.umod
Unreal Tournament 2003
.u2mod
Unreal Tournament 2004
.u4mod