I'll be the first to admit that this is cut and past programming. I've never looked at AD before, and really don't understand it. I suppose that's my next study...
Anyways, This is some test code, which should display the expiry date -- either as something readable, or in ticks -- it doesn't matter. (It's a web form, which is running on the dev webserver.)
What I get instead is: "System.__ComObject "
DirectorySearcher searcher = new DirectorySearcher();
searcher.Filter = String.Format( "(SAMAccountName={0})", "TestA33" );
searcher.PropertiesToLoad.Add( "cn" );
SearchResult result = searcher.FindOne();
DirectoryEntry uEntry = result.GetDirectoryEntry();
String expiry = uEntry.Properties["accountExpires"].Value.ToString();
Response.Write( expiry );