INT 15 U - DESQview/X - ???
        AX = DE29h
        BX = 0001h
        DX = segment of window handle
Return: CF clear if successful
            AX = ???
            DX = ???
        CF set on error
Note:   DESQview 2.50-2.52 are distributed as part of DESQview/X v1.0x.

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