and that alone caused the weird XAMPP control panel problem, produced the error
I have a thought - save the current php.ini by renaming, or whatever you prefer. Re-introduce the default php.ini from the XAMPP DL. IF the problem goes away - bingo - you know what's wrong.
I can think of a situation that would cause the exact thing we see - an "include" statement from a non-XAMPP php extension that assumes the default location (The Apache Software Foundation's installation) for Apache and MySQL.
You can use a tool like WinMerge to compare them line by line (Indeed your whoel install if you chose). Then re-introduce any changes you made that won't cause problems.