Hi there,
For a general response about Xampp and AtoM, please see this recent thread on a similar topic:
Usually, when users encounter a 500 error, our first recommendation is to check the webserver error logs. In a default installation that follows our recommended installation instructions, the links below will tell you how to do this:
However, I'm not sure how a Xampp VM is organized, so the internal path to your webserver may be different.
Hopefully another community member on the forum can offer some suggestions!
Regards,