I've only done this once before at the beginning of starting this whole Mugen thing, but after trying out a new screenpack I like, I need someone to remind me how to get rid of the white writing that shows up.
Go to the mugen.cfg file in the data folder,
then scroll down untill you see............
;-------------------------------------------------------
[Debug]
;Set to 0 to disable starting in debug mode by default.
Debug = 1
;Set to 0 to disallow switching to debug mode by pressing Ctrl-D.
;If Debug = 1, this will be ignored.
AllowDebugMode = 0
;Set to 1 to allow debug keys at all times. Otherwise debug keys
;allowed only in debug mode.
AllowDebugKeys = 0
;Set to 1 to run at maximum speed by default.
Speedup = 0
;Default starting stage for quick versus.
StartStage = stages/stage0.def
;-------------------------------------------------------
basically you change the 1 to 0 next to Debug =
hope it helps