Give details of exactly how you are trying to access your site on the PC that XAMPP is installed on.
Give details of how others not on your network are accessing the site.
Give details of how you are trying to access your site from a network PC that XAMPP is not installed on.
Do you have ZoneAlarm running or the Windows Firewall or an Anti-virus scanner running or anything similar that could block your access? - please check then double check for these blockers and disable temporarily any you find to test your access.
Ports have to be open as well as forwarded.
Make sure your Windows HOSTS files are configured correctly for your PC and your network.
As you know, from your previous posts on the forums that we can only work with you if you relay to us what you see on your monitor, what you have done and what you have tried to do already, otherwise we can only waste time trying to make blind guesses to effect a solution for you.
BTW, XAMPP is not blocking you so it is not really an XAMPP issue because, as you say, there is no problem with the Apache web server.