How do I enable strong password filtering?

 Windows NT 4.0 Service Pack 2 introduced a new password
filter, passfilt.dll, which implements the following new restrictions
Passwords must be at least 6 characters long
Passwords must meet at least 3 of the following criteria
- Uppercase letters A-Z
- Lowercase letters a-z
- Number(s) 0-9
- Non-alphanumeric character (e.g. !, etc.)
Password may not contain your user name or any part of your full name To enable this functionality perform the following on all PDC's (and stand alone's if used). You do not need to install this on BDC's, however you should in case the BDC is promoted to a PDC.
Start the registry editor (regedt32.exe, do not use
Move to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
Double click on "Notification Packages"
Add PASSFILT on a new line (there may be a FPNWCLNT so you should add this after this value). Click OK
Close the registry editor
Reboot the machine
It should be noted you will still be able to set passwords in User
Manager that do not meet the criteria, this is by design as direct SAM updates are not filtered.

Security Administrator More info

     If the above options do not provide enough security for you, download Access manager for Windows.

Access manager provides much more security than standard ways in Windows.

More info

More articles about Security