Password filtering comes in a DLL that you add to your system. To use
it, copy it to your Primary Domain Controller (PDC) and to all your Backup
Domain Controllers (BDCs) in case the PDC fails or roles change. Make sure that
your %SYSTEMROOT%\System32 directory contains the DLL; then adjust one Registry
entry on each domain controller to enable it. Run regedit32, and then
follow these steps:
1. Locate HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
2. Add the following:
Value Name: Notification Packages
Data Type: REG_MULTI_SZ
Data: Passfilt.dll
3. Click OK, and then quit the Registry editor.
4. Shut down and restart NT.
You'll find the source code for this DLL in Microsoft's Knowledge Base
article Q151082 on the TechNet CD-ROM or on the Web,
http://www.microsoft.com/kb.