Hi!
There are problems between using a Linux and Windows based environment. But without an error log output, this is just speculation.
I’m not using XAMPP but WAMPSERVER, which shouldn’t be a big difference but it might differ a bit from my experience.
Please go to your XAMPP root directory / installation and look for a directory called ‘logs’. See if there is a php_error.log, apache_error.log present. You can open those using any text editor.
Can you delete all the content, save it and try Gibbon again? Maybe you will have to disable Apache and XAMPP before saving.
Then please post the content of those logs.
You should as well inform which PHP and Apache version you installed.
The last thing I can think off, is to follow my last post here Restore a server transfer locally
In simple terms, load the access_compat_module or adapt your .htaccess in the Gibbon directory from:
Order allow,deny
Allow from all
to
Require all granted
I hope this helps!