Just use the default Destination folder
as presented, to install it to C:\
then it will install to C:\xampp
Use the default Destination folder
as shown here:http://www.apachefriends.org/images/5509.jpg
Full installation instructions on this page:http://www.apachefriends.org/en/xampp-windows.html#522
If you have installed it to already and want to move it to C:\xampp
only then simply move the C:\xampp\xampp
folder up one level so it now resides in C:\xampp
and then run the setup_xampp.bat
file to have the configurations reset to the new location.
Test all is fine by going to http://localhost
and trying out the demos before proceeding with anything else.
Read the readme_en.txt file and the FAQ (link)