bbwin

In order to limit the size of the uploaded logfile, you can edit the client-local.cfg file.
Use a text string or regular expression to exclude these lines from the uploaded log file.
Remark: You can only filter on the text (value=) of an error.

In local mode: edit the BBwin file
<msgs>
<match logfile="System">
<ignore logfile="System" value="(text string)">
</msgs>

In central mode: edit the client-local.cfg file
eventlog:system
ignore [text string or regular expression]

example of client-local.cfg:
[win32]
eventlog:security
ignore success
ignore Success
ignore User Logoff
eventlog:system
ignore [some regular expression]


Tips:
regular expressions are case sensitive.
you can use the Mozilla Firefox regular expression tester plugin https://addons.mozilla.org/en-US/firefox/addon/2077 to test the syntax of your expression.
see also: http://en.wikibooks.org/wiki/System_Monitoring_with_Xymon/Administration_Guide#Install_Xymon_client:_BBWin_0.12