Never overwrite events in the security log because the log is full for a reason. Digital evidence is extremely
important and the security logs give a chronological sequence of events. The log could be full for a few reasons: 1) A sysadmin isn't performing their job correctly; 2) A possible malicious activity on your system; 3) A misconfigured system that generates events.
In the event you get an error that identifies that you cannot log on to either Windows 2000 or Windows XP, then contact the security manager because it means the sysadmin is not performing their job correctly.