Carlos
The best way to delete all the Event Viewer log files, including the combined administrator log, courtesy of Windows Seven Forums at this site
http://www.sevenforums.com/tutorials/25480-event-viewer-one-click-clear.html?ltr=E
Copy and paste the following twelve lines to Notepad, save it as ClearAll.bat. Run it by right-click or press and holding it and choosing Run as Administrator. Here are the twelve lines:
@echo off
FOR /F "tokens=1,2*" %%V IN ('bcdedit') DO SET adminTest=%%V
IF (%adminTest%)==(Access) goto noAdmin
for /F "tokens=*" %%G in ('wevtutil.exe el') DO (call :do_clear "%%G")
echo.
echo goto theEnd
:do_clear
echo clearing %1
wevtutil.exe cl %1
goto :eof
:noAdmin
exit