Hi Panos83,

You may have to stop the service (IIS Admin service) which is recording data to exsecars.log and ersecreg.log first, but there's no danger in deleting those files.  They will be recreated to log new activity.

Are they growing to an unnecessarily large size?  Be sure that debugging has not been left on.  This article may help, scroll down to the section about "DebugLevel":

How to debug the Symantec Endpoint Protection Manager console in Symantec Endpoint Protection 11.x

Also: the size of these files will be smaller in SEP 11 MR4 and later.  Be sure you are not running an earlier version than that!  And keep an eye out for SEP 11 RU5 (the new designation for MR5) which will be released in the next week or two.  All customers are encouraged to migrate to the latest version, to take advantage of the most recent enhancements and improvements!

Thanks and best regards,

Mick