unable to install wordpress theme

I have successfully installed wordpress on my local machine. I want to use the vantage theme for my demo website. I am installing theme from Appearance-> themes-> add new themes. As I typed the name of my required theme, the themes get displayed and when I clicked install button the downloading starts but after few seconds an error arise which says,
Fatal error: Maximum execution time of 30 seconds exceeded in G:\xampp\htdocs\wp_physio\wp-includes\class-http.php on line 1597. Can anybody resovle this.

Also to mention I have successfully installed the same theme in the past on the same machine in different website