Ddraw tweaks

No primary SYSTEMMEMORY	NOSYSMEMPRIMARY	DirectDraw applications have much better performance if they can operate on system memory rather than video memory, particularly when reading surface memory. Since the virtual primary surface has to be read before it can be transferred to the actual primary surface, it's best to use system memory offscreen surfaces whenever possible. Unfortunately, some programs request hardware acceleration functions that are only available for video surfaces. This flag forces the virtual primary surface to be created in system memory, sacrificing performance for compatibility.
No backbuffer SYSTEMMEMORY	NOSYSMEMBACKBUF	Similar to the NOSYSMEMPRIMARY flag, but applied to the backbuffer surface. It's rare to need both of these flags, and which one to use depends on where the application performs the accelerated functions.
Lock/Unlock Pitch Fix	FIXPITCH	Some programs ignore the pitch value returned by the DirectDrawSurface::Lock method and fill the graphics buffer according to an incorrect predetermined pitch value. This discrepancy is caused when DxWnd creates virtual surfaces with varying pitch values that may not correspond to the original values when creating the surface on a different memory type (system memory and video memory). When this is happening to a hooked program, some elements may appear diagonally skewed. Note how the left border of the text widget in the figure below goes down and to the right rather than straight down, distorting the contained text as well. This flag resolves the issue by copying the graphic scan lines to the proper memory offset.
Width not power of 2 fix	POWER2WIDTH	Some programs produce texture surfaces of odd sizes, which are generally not supported but can be detected when the textures have an incorrect aspect ratio. This flag resolves the issue by copying the graphic scan lines to the proper memory offset. The most notable example of this issue is in Midtown Madness.
Fix ddraw refcount	FIXREFCOUNTER	Decrement the reference counter of some objects to properly track all of DxWnd's service objects.
Return 0 refcount	RETURNNULLREF	Always return a 0 reference counter when a surface or DirectDraw session is released.
Suppress overlay capability	SUPPRESSOVERLAY	Prevents the game from detecting any hardware overlay capability. Hardware overlay is very efficient, but not very flexible. If you run a program with hardware overlay in a window, you may be able to reposition and resize the window, but the blitted surface (the content of the window) doesn't move or change. This flag makes programs ignore hardware overlay capability so that you can move or stretch the window with expected results. The most notable example of this issue is in Moto Racer 2.
Set minimal caps	MINIMALCAPS	Simulates minimal hardware capabilities similar to what's available by the VirtualPC or VMWare emulators. Some older games may not support advanced features, in which case this flag can improve the rendering process and eliminate some artifacts.
Deinterlace movies	DEINTERLACE	Interlaced movies on old games would improve their frame rate by only showing the odd horizontal lines of the video, leaving even lines black. The black lines weren't very noticeable on old monitors, but the effect becomes more pronounced on modern computers. This flag detects interlaced movies and interpolates the lines above and below each black line to approximate a full video, improving the video quality at the cost of some extra CPU usage.
Set ZBufferBitDepths capability	SETZBUFFERBITDEPTHS	The dwZBufferBitDepths is an obsolete field in the DirectDraw surface descriptor. It is no longer set and should be ignored, but some old programs rely on the value of this field and may crash if the field is empty (contains the null value). This flag copies the value returned by the GetCaps method and places it into the dwZBufferBitDepths field. The most notable example of this issue is in Mech Commander 2.
Limit ddraw interface	LIMITDDRAW	Instead of using a specific version of DirectDraw, some programs simply request the most recent version available on the machine. Using a version of DirectDraw that is significantly newer than what was available when the game was developed may have poor results. This option hides newer versions of DirectDraw from the hooked program, basically allowing you to manually specify which version of DirectDraw the program should use. Choose a maximum DirectDraw version from the drop-down menu located near this option.
Forces HEL	FORCESHEL	Forces Hardware Emulation Layer.