Get one of the many programs that take the max resolution windowed mode (like, windowed mode of 1920x1080 when that's your desktop resolution) and gets rid of the borders to make it fullscreen, while letting you alt+tab functionally.
I use ShiftWindow for FFXIV. Google it. It works with any game.
R.I.P Teraud, Dragoon main on Seraph (2004-2007)
R.I.P. Atli, Blue Mage main on Seraph (2007-2008)
R.I.P. Silje, Beastmaster main on Odin (2008-2008)
R.I.P. My Final Fantasy XI Account forevahz
Back on ZAM for FFXIV!