If you can't use your mouse while playing Duke in DOS, try what I did. Since I have Win 95, after I restart in DOS there is C:\Win> on the screen.
1) Change the directory to C.
C:\Win>cd c:\
2) Change again into your Duke directory.
C:\>cd Duke3d
3) Type mouse.
C:\Duke3d>mouse
4) When Enter is pressed, I get a few lines of computer jargon which say:
Mouse driver installed.
You can go play your heart out like in Doom!!
Q: Where can I get the 3DFX patch for Duke3d?
A: There is no 3DFX Patch for Duke Nukem 3D and there never will be.
Q: Why not?
A: Because Duke is not really 3D. It doesn't use polygons. It uses
sprites instead. ie. If you circle around a vase it looks the same.
Q: But it says Duke Nukem "3D" on the box.
A: Yes it does. But it is not true 3D. This Duke is version 3 being
in 2D; they made it easier to remember by shortening it to Duke 3D.
Adding further to your disillusionment:
There is no Santa Claus.
The Titanic sinks at the end of the movie.
"RoseBud" was the name of his sled.
Darth Vader is Luke Skywalker's father.
Q: So when is the patch coming out?
A: Never.
Q: So what you're really saying is that they'll come out with one later,
right?
A: No. There will Never Ever Ever be a 3DFX patch.
Q: You're just trying to fool us and you just want to keep the patch to
yourself, don't you?
A: No!! There will NEVER, NEVER, NEVER, NEVER, EVER, EVER, EVER,
EVER, EVER be a 3DFx patch for Duke Nukem. NEVER! EVER!
Q: Aha! So they're working on an OpenGL patch then, right?
A: No. Duke 3D is old now (1998) and they're working on Duke Forever
(Duke ver. 4).
Q: But there's a 3DFX patch for Blood, and that game used the Duke
engine!
A: This isn't Blood, and anyway, that engine is MODIFIED.
Answers provided by NutWrench at the alt.games.duke3d newsgroup