得到内存的 Status

　　function GetMemorySts:TMemoryStatus;
　　begin
　　ZeroMemory(@Result,SizeOf(Result));
　　Result.dwLength:=SizeOf(Result);
　　GlobalMemoryStatus(Result);
　　end;

TMemorySatus 的结构如下：
_MEMORYSTATUS = record
dwLength: DWORD;
dwMemoryLoad: DWORD;
dwTotalPhys: DWORD;
dwAvailPhys: DWORD;
dwTotalPageFile: DWORD;
dwAvailPageFile: DWORD;
dwTotalVirtual: DWORD;
dwAvailVirtual: DWORD;
end;
{$EXTERNALSYM _MEMORYSTATUS}
TMemoryStatus = _MEMORYSTATUS;