   Getting D3D apps to work on any bit-depth.
  If D3D applications can''t work on 24 bit mode and a computer doesn''t have 32-bit mode, then how come whenever I play a 3D game on 24-bit mode, there''s no error? 
  1) 24bit backbuffers were possible in older versions of DirectX.2) 24bit is slower than 16bit or 32bit so generally not a good choice.3) Some games don''t use Direct3D.4) Not many cards actually support 24bit - IIRC it''s only Matrox ones that do.5) How are you determining that the other games you''re playing are actually using 24bit? - if they''re full screen they''re very likely to be checking the caps changing the mode when they CreateDevice()6) So it''s only windowed apps that can''t work when the desktop mode is set to 24bit - in those cases I just bring up a dialog box at app start time to inform the player that the game won''t work with windowed mode on their desktop it also offers to change their desktop mode for the durarion of the game for them. The same is done when they have their desktop set to 256 colour (or lower).  