I'm having the exact same problem too...
I've installed XAMPP, and i've been working with it for about 4 months,
and things have been going fantastically, (for me...)
I can view my 'creations' and websites through http://localhost/mysite
and through http://127.0.0.1/mysite
, yet as soon as I ask a friend to check out my site, (and I send them to http://myipaddress/mysite
they get an error message... This is NOT good....
I've asked some people, (on these forums) and they've told me to check through http.conf, enabling 'allow outside connections' but i couldn't find the options...
Please someone HELP!