Block computers with multiple erroneous login attempts(Windows XP, Vista, 7)

               When logging in to an account an unauthorized person can try passwords frequently. This is unsafe. Therefore, you would want to automatically lock the account after a number of incorrect entries.
               The default Windows settings enforce only simple passwords and limited protection. It makes more sense to lock the user account for a certain period after several failed attempts, with a security policy.
                If you have the Business, Professional or Ultimate versions of Vista or Windows 7, the process is easy. In the search box in the Start menu, type ‘Local Security Policy’ and start the program that is found. Now click the on the left on ‘Account Policy’ and then on ‘Account Lockout Policy’. To change the lock settings change the ‘Account Lockout Threshold’ value to ‘3’ invalid login attempts, for example, and confirm with ‘Apply’. Windows now automatically enables the parameters ’Account lockout duration’ and ‘Reset account lockout’ for each of 30 minutes. Confirm the open dialogue box with ‘OK’ and check the changed security policy settings. Do not extend the account lockout duration. To defend against deliberate attacks, this amount of time is sufficient. Close all dialog boxes. Now after the defined number of invalid login attempts, the user receives a message that the account at this point of time is locked.
              For other versions of Windows, the setting can be made only from the command line. Just type ‘cmd’ into the search box, right click on ‘cmd.exe’ and select the context command ‘Run as administrator’. Type the command ‘net accounts’ to ask for the current configuration.
              Here are the important parameters for the lockout, lockout duration and reset checking period. Set this with the commands ‘net accounts / lockoutthreshold:3’, ‘net accounts / lockoutduration:30’ as well as ‘net accounts /lockoutwindow:30’. Finally, you should double check that all values are typed correctly, since incorrect settings in extreme cases may permanently block your account. For emergencies, you should always still have an additional hidden administrator account set up.