I just tried to update XAMPP for Windows to version 1.6.7, using the installer version.

Somehow, it did not work without removing the old version first: Apache changed status to “Running”, then suddenly stopped again. There was no way I could access the admin panel. Same happened with MySQL.

After removing the old version, Apache started (as did MySQL), but clicking on “Admin…” resulted in a “500 Internal Server Error”.

Here is the (pretty simple) solution:
An old .htaccess still remained in “…/XAMPP/htdocs/xampp/” which delivered the error. Deleting it did the trick.

And here is a reminder for me:
Permalinks don’t work by default in XAMPP because ModRewrite is not loaded… open “…/XAMPP/apache/conf/httpd.conf” and remove the “#” before LoadModule rewrite_module modules/mod_rewrite.so… stupid!