make sure its is a new installtation of indexu, you cant copy the files from your already installed webserver.. yet. you have to put a fresh copy of indexu in your new folder on xampp. then make sure you have deleted you .htacess file (or else you get 500 error),then create your indexu database under the xampp control pannel in phpmyadmin, once you have done this run the installation file for indexu, should be
http://localhost/new/install/install.php
go for a new install and enter the correct data base details ie:
user : root
password: (as default there is no password)
database path :
http://localhost
once you have installed delete the install folder
then load up your indexu on xammp, and copy the templates you need from your online indexu to your xampp indexu themes folder