not right, left in that orange column
just kidding.
Please take a look into your
C:\xampp\htdocs\xampp\lang.tmp file.
If the file doesn't exist, please create one.
If it's content is not just
en for english, please change it to
enThe other way would be to first go to the main page
http://localhost/xampp/, you should have been redirectled to the splash site
http://localhost/xampp/splash.php where you can choose your language.
If that doesn't work too, then you should maybe reinstall your whole XAMPP.