Make a full backup of your Xampp installation.
Then uninstall Xampp, install new Xampp 1.7.1.
After then port all changes from old Xampp configuration files (httpd.conf & extra/*.conf, php.ini, my.cnf) to the new installation (do *not* copy configuration files from old installation, use a text editor instead).
Copy all contents of your applications to the new Xampp (DocumentRoot i.e. htdocs, maybe several, ALIASes, cgi-bin etc.)
Replace MySQL data folder by the backuped data folder.
Then start Xampp and look if everything runs fine.