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I recently went from 1.3 to 2.3.3.
you can jump from 2.0.13.2 or better by using the upgrade option that comes with the full 2.3.3 download. Read the release notes for specific instructions but basically you make a modified html/htdocs directory, copy it on to your existing XOOPS file structure and run the upgrade script (in /upgrade) you need for the version you are upgrading from.