First look in the logs and see what they're filling up with. Then clear them. Gonna need more info before suggesting anything, but I'm assuming you're talking about NT event logs, not Exchange logs, since that's usually what that message refers to.
Might want to set a circular log for anything older than 1 or 2 days so they don't keep filling up.
As pcoyak said there is a reason why the event log is filling up. If there are a lot of error messages, deal with the error, then the messages will go away. If your doing alot of logging of things that are working then either reduce the level of logging that is done, or set the event log to overwrite when its full, but if you need these logs be carefull what you overwrite.
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