Alfred, it all depends on what version of XAMPP from and what version to.
If your version is fairly recent then the upgrade file on the Apache Friends web site will usually inform you as to which versions the upgrade will work on.
If you have an very old version then uninstall the old version, backing up your configuration and database files first then delete the old version's directory (or as I do, rename the directory to copy of etc. so I don't lose any of my old files).
A new install of the latest version is then recommended in this case.
just over write the backed up configuration files if you have installed a new version as they may have additional configuration entries for the latest versions of the XAMPP components.
But you can edit the new configuration files and include your previous edits from the old configuration files in them.
Sounds a bit messy but remember that in the latest version of XAMPP they include the latest and greatest components which usually are not backward compatible.
It often pays, for ease of upgrading, to keep abreast of the releases and use the upgrade files on Apache Friends web site. If you get too far back in versions then it usually means going through this messy proceedure to catch up.
Same with your database files.
Best with these to dump them using phpMyAdmin and be aware of the upgraded MySQL compatibility issues. In phpMyAdmin you can dump using various MySQL versions for compatibility.
I use the 7Zip XAMPP versions as I can then compare the various changes that have taken place plus I can locate XAMPP in a drive/directory of my choosing. Future upgrades I find much easier using this method.
I did a search in the English forums for some old posts on this subject using upgrade as the keyword and izzy as the Author as I seem to remember answering this issue before.
Hope this helps a bit as there is not much info, as you say, about upgrading.
Good luck with it.
Take a look at the new DeskTopXampp
launch control posted by ridgewood
http://community.apachefriends.org/f/viewtopi ... 967#103967
launch control for XAMPP
is available here:
I highly recommend DTX.