Clears the specified event log, and optionally saves the current copy of the logfile to a backup file. The method returns ...

Clears the specified event log, and optionally saves the current copy of the logfile to a backup file. The method returns an integer value that can be interpretted as follows: 
0 - Successful completion.
8 - The user does not have adequate privileges.
21 - Invalid parameter.
Other - For integer values other than those listed above, refer to Win32 error code documentation.