Instead of trying to modify it after the fact, simply load your .txt file in WordPad, make the formatting changes you require, then save it in .rtf format. You can then use this file as your InfoBeforeFile
directly, without using any code.
Edit: if you want to change the background colour of the entire memo then you'll still need one line of code. For example:
[Code]
procedure InitializeWizard();
begin
WizardForm.InfoBeforeMemo.Color := clBlack;
end;