There are only two ways to change modes once the device is created:
1) Destroy the device, and start again - this way you lose all your textures, vertex buffers, index buffers, state blocks, state settings, everything.

2) Call Reset - this way you lose all your state blocks, state settings, and any textures, vertex buffers or index buffers except those which were put in D3DPOOL_MANAGED or D3DPOOL_SYSTEMMEM.

It''s your choice.

John B

hey, thanks for all the advice especially bout the managed_pool thing!! probably there''s no such way to stop CreateDevice(...) in going fullscreen,

i''ll just probably call it with presentparams.windowed = true, this way the game window will still be hidden till i call create device again to init in fullscreen,

Set Windowed parameter to TRUE and get a windowed device suitable for debugging.
Set it to FALSE and get a fullscreen device suitable for end user.
Implement a dialog or some other settings mechanism to allow the end-user to choose between windowed and fullscreen mode. All of these are done via CreateDevice.
Implement a toggle in your program to switch between windowed and fullscreen modes back and forth (via Reset).
But don''t initialize windowed mode and then immediately switch to fullscreen. Why would you want to do this anyway?

alright, thanks!!