WinExec

//声明
WinExec(
  lpCmdLine: LPCSTR; {文件名和参数; 如没指定路径会按以下顺序查找: 程序目录/当前目录/System32/Windows/PATH环境变量}
  uCmdShow: UINT     {启动选项}
): UINT;

//返回值:
大于 31                    {调用成功}
等于 0                     {内存不足}
ERROR_FILE_NOT_FOUND = 2;  {文件名错误}
ERROR_PATH_NOT_FOUND = 3;  {路径名错误}
ERROR_BAD_FORMAT     = 11; {EXE 文件无效}

//uCmdShow 参数可选值:
SW_HIDE            = 0; {隐藏, 并且任务栏也没有最小化图标}
SW_SHOWNORMAL      = 1; {用最近的大小和位置显示, 激活}
SW_NORMAL          = 1; {同 SW_SHOWNORMAL}
SW_SHOWMINIMIZED   = 2; {最小化, 激活}
SW_SHOWMAXIMIZED   = 3; {最大化, 激活}
SW_MAXIMIZE        = 3; {同 SW_SHOWMAXIMIZED}
SW_SHOWNOACTIVATE  = 4; {用最近的大小和位置显示, 不激活}
SW_SHOW            = 5; {同 SW_SHOWNORMAL}
SW_MINIMIZE        = 6; {最小化, 不激活}
SW_SHOWMINNOACTIVE = 7; {同 SW_MINIMIZE}
SW_SHOWNA          = 8; {同 SW_SHOWNOACTIVATE}
SW_RESTORE         = 9; {同 SW_SHOWNORMAL}
SW_SHOWDEFAULT     = 10; {同 SW_SHOWNORMAL}
SW_MAX             = 10; {同 SW_SHOWNORMAL}

from http://www.cnblogs.com/del/archive/2008/02/13/1067871.html

//举例, 启动记事本:
procedure TForm1.Button1Click(Sender: TObject);
begin
  WinExec('notepad.exe', SW_SHOWNORMAL);
end;