Your contact form has 3 minor errors according to my validator as follows:
Line 85:The attribute: onsubmit does not conform to upper/lower case requirements.
Line 86:The tag name: "left" Not found in currently active versions.
Line 89:The tag: "table" doesn't have an attribute: "height" in currently active versions.
However, this has nothing to do with your problems!
The problem is the mail function in Xampp. Truth is I've never made it work for me either!
1. By default, the mailer is not started when XAMPP starts. Go to the Xampp control panel (Start, Programs, Apachefriends, xampp, Control Xampp sever Panel
on my system.)
2. Click the Mercury 'Start' button
3. Click 'Admin'
This step you need to work out for yourself/get further advice about setting up the mail server. Sorry I cant help with that
Anyway, good luck with it - I hope that helped a little!