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2.: I have written down that wish wrongly. I meant i want to be able to only have the text visible (and maybe menu bars since that cannot be prevented as you said) and have a transparent background (the thing that´s white and you can change the background in the settings). I tried putting a transparent background but that didn´t do the trick.

The transparency feature mIRC uses only allows it to set the transparency level for the whole window. It cannot set arbitrary levels of transparency for different parts of a window. What you are asking for is far more complicated I'm afraid, ie. a transparent background with non-transparent text. I am not sure it would even be possible with the way mIRC currently display windows.