This is my suggestion, just posted a few threads down. It's the easiest way...
well, what i would suggest is this. create a folder and call it newforum. install all your files, and COPY (NOT MOVE) the config file from the old copy to the new location. access the direcotry and it should be working after you remove the install and contrib folders. Then rename your current board location from (i.e/forum/) to /oldforum/ and then make the newer version the original name (/forum/ or whatever) . then run the update_to_latest.php's from 2.0.12 to current to update the DB tables. Install easymod and reinstall mods
Here is another way, but i prefer mine because it keeps everything active in case theres a problem with the new files.
There is a way to start from scratch, but keep your current database and update your forum at the same time. If you have any Mods installed, this *will* remove them.
Backup all your forum files
Go into the Admin Panel and set the style to subSilver
Download the Full Package 2.0.20 from this site
Delete all the files in your forum folder *except* config.php
Upload the Full Package 2.0.20 *except* for the config.php file
Point your browser to:
http://www.yoursite.com/forum/install/u ... latest.php
***Note: Replace yoursite.com and forum with your stuff
Delete the /install and /contrib folders