If you receive a message stating that the Security Log is full when you log into Windows 7, Vista or XP, follow  steps below to eliminate the message.

Steps to be done in Windows 7 or Vista:

1. Log in into computer as an Administrator.

2. Start menu > Control menu > Change view to Large or Small icons.

3. Administrative Tools > Computer Management.

4. In the left pane double-click Event Viewer and then Windows Logs.

5. Right-click Security and choose Clear Log. You'll be prompted whether to save or not Log file. After the prompt, log will be cleared.

Windows XP:

1. Log in into computer as an Administrator.

2. Start menu > Control Panel > Administrative Tools > Computer Management.

3. Choose Event Viewer > expand the node and click on Security.

4. Go to Action menu and select Clear All Events and then click No when being prompted to save the log.