Originally Posted by Dwarden View Post
they works for me ...

for
STEAM version of ARMA 2 Demo / ARMA 2 full
retail version of (must be started via add-non STEAM game) ARMA 2 Demo / ARMA 2 full

BUT if you are VISTA user YOU need take part in STEAM beta client program

on STEAM UI on top there is menu, choose VIEW > SETTINGS > in beta section choose CHANGE ... and enter "STEAM Beta Client"
Restart STEAM and now overlay will work with VIsta's Direct9EX which ARMA 2 uses by default

for more technical details see http://forums.steampowered.com/forum...d.php?t=903468
Fix for overlay problems with Vista users and the demo and full game.