If you have successfully installed the xampp you can got to windows,
START -> ALL PROGRAMES -> APACHEFRIENDS -> XAMPP -> CONTROL XAMPP SERVER PANEL
to view the control panel. This will list all the modules which is currently running on your machine. Check module apache , if its not indicating as running click on the Start button to start the apache server.
FYI: there is a check box in front of every module which says Svc. check it so next time you dont have to manually start the server instead now it will start as a windows service.
Hope this helps,
Best regards,
niroshan