ManagementClass   mcs=   new   ManagementClass( "Win32_UserAccount ");   
ManagementObjectCollection   moc   =mcs.GetInstances();   
rchbx.Clear(); 
foreach(ManagementObject   mo   in   moc)   
{   
string   user= " "; 
user=mo.GetPropertyValue( "Name ").ToString(); 
rchbx.AppendText( "用户名: "+user+ "\n ");   
user=mo.GetPropertyValue( "Domain ").ToString(); 
rchbx.AppendText( "所属域: "+user+ "\n ");   
}   
//添加对System.Management的引用

------解决方案--------------------
设置密码过期时间就可以了，费什么事要写程序监控啊。另外正常方法是取不到密码的