I am using following code to access active directory in my Windows application. 1 Dim path = "LDAP://10.10.20.69/OU=dev,DC=abcde,DC=com" 2 Dim userName = txtxUser.Text 3 Dim sUserName = path & "\" & userName 4 Dim passWord = txtPWD.Text 5 6 Dim dirEntry As DirectoryEntry = Nothing 7 Dim searchObject As DirectorySearcher = Nothing 8 Try 9 10 dirEntry = New DirectoryEntry(path, sUserName, passWord) 11 12 13 searchObject = New DirectorySearcher() 14 15 searchObject.SearchRoot = dirEntry 16 searchObject.SearchScope = SearchScope.Subtree 17 searchObject.Filter = "(sAMAccountName=" & userName & ")" 18 searchObject.PropertiesToLoad.Add("CN") 19 20 Dim colQueryResults As SearchResult = searchObject.FindOne() 'error throwing in this line 21 22 23 If colQueryResults IsNot Nothing Then 24 MessageBox.Show("Authentication success") 25 Else 26 MessageBox.Show("Authentication failure") 27 End If 28 Catch ex As Exception 29 MessageBox.Show(ex.ToString) 30 Finally 31 dirEntry.Close() 32 searchObject.Dispose() 33 End Try When I run this code in Windows 2000 it is working fine. But When i try in 2003 machine it is throwing an exception like this : System.Runtime.InteropServices.COMException (0x80005000): Unknown error (0x80005000) at System.DirectoryServices.DirectoryEntry.Bind(Boolean throwIfFail) at System.DirectoryServices.DirectoryEntry.Bind() at System.DirectoryServices.DirectoryEntry.get_AdsObject() at System.DirectoryServices.DirectorySearcher.FindAll(Boolean findMoreThanOne) at System.DirectoryServices.DirectorySearcher.FindOne() at ADErrortester.Form1.Button1_Click(Object sender, EventArgs e) Anybody can help in this...?