typedef struct _RTL_USER_PROCESS_PARAMETERS
{
     ULONG MaximumLength;
     ULONG Length;
     ULONG Flags;
     ULONG DebugFlags;
     PVOID ConsoleHandle;
     ULONG ConsoleFlags;
     PVOID StandardInput;
     PVOID StandardOutput;
     PVOID StandardError;
     CURDIR CurrentDirectory;
     UNICODE_STRING DllPath;
     UNICODE_STRING ImagePathName;
     UNICODE_STRING CommandLine;
     PVOID Environment;
     ULONG StartingX;
     ULONG StartingY;
     ULONG CountX;
     ULONG CountY;
     ULONG CountCharsX;
     ULONG CountCharsY;
     ULONG FillAttribute;
     ULONG WindowFlags;
     ULONG ShowWindowFlags;
     UNICODE_STRING WindowTitle;
     UNICODE_STRING DesktopInfo;
     UNICODE_STRING ShellInfo;
     UNICODE_STRING RuntimeData;
     RTL_DRIVE_LETTER_CURDIR CurrentDirectores[32];
     ULONG EnvironmentSize;
} RTL_USER_PROCESS_PARAMETERS, *PRTL_USER_PROCESS_PARAMETERS;

Windows Vista Kernel Structures