得到一个临时的文件名称（使用GetTempFileName API函数）

function GetExePath: string;
begin
  Result := ExtractFilePath(ParamStr());
end;

function GetTempFileName: string;
var
  vPath: string;
begin
  SetLength(Result, );
  GetTempFileName(PChar(GetExePath), PChar('~'), , PChar(result));

  vPath := GetExePath + 'temp\';
  if not SysUtils.DirectoryExists(vPath) then
    SysUtils.ForceDirectories(vPath);
  result := PChar(Result); //去掉多余的空字符
  Result := vPath + ExtractFileName(Result);
end;

http://blog.csdn.net/shuaihj/article/details/7108792