[SKAzini]

Basically, when I alt-tab the game, in or out, my screens flickers like 5 times before actually tabbing. Why is this?

[Mauzen]

Your ingame resolution isnt the same as desktop, is it?
Your graphics card or monitor might need some switches to change the screen resolution. Not much you can do about that, maybe updating graphics drivers might help, if yours are very old.