You should back up all of your existing files before launching the Community Server 2008 upgrade tool.
You cannot upgrade directly from Community 2007 to Community Server 2008. If you do not have Community Server 2007.1 installed, you must first upgrade to Community Server 2007.1, then from 2007.1 to 2008. To upgrade to Community Server 2007.1, go to http://get.communityserver.com/download/cs20071up.
Procedure
If you have not yet read the upgrade notes, Community Server provides you with a link to the notes.
The locations show the default paths for your existing galleries and post attachments.
If your existing site has virtualization, a screen displays that reminds you to read the upgrade notes about how to upgrade a site that has virtualization.
If your site does not have virtualization, the upgrade tool describes the upgrade process for you.
After the upgrade is complete, you can check the log file to see all the actions taken by the upgrade tool during the upgrade process. If any errors occur during installation, you can use the information in the log file to troubleshoot the problem by posting the information on the dev.cs.com forums and requesting assistance.