On further thought, I can't believe that XAMPP would modify the Apache conf files so massively as to eliminate the extras subdirectory, the httpd-vhosts.conf file and the link between the two at the end of the httpd.conf file. I believe you didn't find them but please look again. If you have a good search function, search for <VirtualHost and it should show you your httpd.conf as well as the httpd-vhosts.conf files (perhaps even more files but I hope not).
I have used only the basic information required by the <VirtualHost> block and have provided that above. SPecifically, you're lacking the IP address:port, the server name (in some) and the server path (in others). You should not repeat the localhost (which should be in the httpd.conf as it's the default) and ... well, as a student, I'll ask you to check and match the format for your Virtual Hosts data. Should that fail, please post the revised code and I'll help you get through it.
As an aside, the FREE chapter of Kevin Yank's book is a great installation tutorial (albeit, the ancient version I first used was a bit out of order and WinDoze has changed drastically - keep out of the Program Files directory at all cost and be sure to specify the server correctly - 127.0.0.1 and localhost - when installing!). I prefer to install my daemons (MySQL, Apache, PHP and PHPMyAdmin - a great crutch for MySQL) individually rather than use a "canned app" like XAMPP but that was what you had specified.