I am learning Drupal 8 and have installed Drupal 8.1.2 version on XAMP. No theme files are included when page is loaded (viewed source).

When trying to solve this, I changed theme from default bartik to stark. Still no theme files are loaded. And now I am trying to switch it back to bartik, but I am unable to.

"Bartik is now the default theme." is displayed but Stark 8.1.2 (default theme) is default theme.

See screenshot below: