I've just started rebuilding my graphics engine and in order to test the different resolutions I need to make it fullscreen, but when I change d3dpp.Windowed to FALSE Visual Studio tells me the program's triggered a breakpoint (Which I didn't set).

The dialog says: Program.exe has triggered a breakpoint and asks me to break or continue.

Here's the DX debug log.

Direct3D9: (ERROR) :Invalid value for BackBufferFormat. ValidatePresentParameters fails.

D3D9 Helper: IDirect3D9::CreateDevice failed: D3DERR_INVALIDCALL

Direct3D9: (INFO) :MemFini!

Direct3D9: (WARN) :Memory still allocated! Alloc count = 5

Direct3D9: (WARN) :Current Process (pid) = 00000554

Program.exe has triggered a breakpoint

Direct3D9: (WARN) :Memory Address: 003654e8 lAllocID=1 dwSize=000047f8, (pid=00000554)

Direct3D9: (WARN) : Stack Back Trace

Any ideas on how to fix this?