You are not the only one with a slow Joomla - seems half the world has a slow Joomla.
From what I have read up on so far the issues are with Joomla and it's settings not the server as some have used the same server with different installations of Joomla differently configured with some slow and some fast - you have to do some reconfiguring to run on more recent versions of server software than you previously ran Joomla on.
You can, if you wish, install an older version of XAMPP with a more closely matching set of server software versions to what you previously found to be faster for Joomla:
The XAMPP For Windows Archive
English translated page of XAMPP archive contents
There may also be some server side tweaking that can be implemented but without more info on your issue that would only be a stab in the dark.
Read this Joomla Forum Thread
and you will see a number of cures from a number of different users - be warned it is a long thread and needs to be read in full so you can experiment with the various fixes.
The author of This Article
seems to have found some solutions:
Also this Google Search
may have even more clues for you.