Okay, believe me, this is my last try to explain you how you can access your files.
Here is an example.
Let's say you have installed xampp directly in the root of your HDD C: partition
You have a directory C:\xampp\
You have a directory C:\xampp\htdocs\ <-- THIS IS YOUR DOCUMENT-ROOT FOLDER!!!
So, if you type in http://localhost/
your Webserver search for files in C:\xampp\htdocs\ first.
If you type in your Browser http://localhost/MyFooProject/
your Webserver searches in C:\xampp\htdocs\MyFooProject\ for files.
If you type in your Browser http://localhost/MyFooProject/test.php
your Webserver searches for the file test.php in your C:\xampp\htdocs\MyFooProject\ Folder
I'm so sorry, i can't explain it more clearly.
If you don't understand it by now, maybe JonB can explain it better. His english is much better than mine