if anyone got performance issues with
UT99 (G.O.T.Y.) . Maybe this can help.
I use the CD-Rom version of the game and
have tryed one of these solutions
on my old Windows Vista PC (replacing the OpenGl.dll) . The game run's pefect now.
There are other Dll's for Win10 toohttps://www.gog.com/forum/unreal_series ... workaround