让登陆的用户扮演另外的用户，很不错的代码。-Substitute User (access privlieged pgms while logged in on a non-privileged account). Allows a logged-in user to temporarily impersonate another (including Administrator) without logging out and in again. Similiar to UNIX su(1) command. Useful sample for NT Security APIs. Minimum NT 3.51, build 1057 only