One way to increase password security is to increase the number of characters used in the password. As an administrator, you can enforce a minimum password length on your users in Windows XP to increase the security of your system.

Open up the Control Panel, then open Administrative Tools, then open Local Security Policy. Once there go into the Account Policies section and double click on Password Policy. Once this opens find the Minimum Password Length entry and double click on it to set a minimum allowed number of characters to be used for passwords on your system.

Once done editing, click OK to save your changes.