You can you can find download link on this page:

http://www.lizard-labs.net/log_parser_lizard.aspx.

Or just click on this link to download latest version of the product:

http://www.lizard-labs.net/Download.aspx?fname=LogParserLizardSetup.msi

To upgrade the product version you have to uninstall previous one from Control Panel and install the new one. The files Queries.xml and Constants.xml will remain from your previous version so you will keep all your queries in the latest version of LPL. If you want to install these files from the installer you will have to delete them manually from installation folder