If you get a message ‘security log is full’, can take the following steps….
1. log in as administrator
2. right-click ‘my computer’ icon and select ‘manage’
3. in the computer management window, expand ‘system tools’, then expand ‘event viewer’
4. select the ‘security’ entry
5. from the computer management window menu, select ‘action’, then ‘clear all events’
6. click ‘yes’ to save a copy of the log, or ‘no’ to clear the log completely