I don't know what it is that I did, I was trying some new themes in my Windows so I installed this patch that was needed to do it, then I fiddled with some themes. I don't where in the process but somehow my letters are almost white (very light gray), I can barely see what I'm typing right now.
Changing only the back panel of the windows would already help. Although I now returned to the default Windows theme, somehow the programs menu of the taskbar (I use Classic Shell) is still black from a theme I tried and it's actually much more readable than the white background, which is barely readable at all. I'm on Win 8 Pro x64.