Upgrading

The local database, where all your logs are saved, is installed, by default (look at Quick start for changing the location), to the "database" folder, under your log4day installation folder.
So the better way to do an upgrade is to rename your log4day installation folder, i.e. to log4day_old, then unpack the new version and copy the database folder from the saved folder.
If you have a log4day.preferences file or log4j.xml file, then copy them from the old folder.