Is there an option in the windows version of Apache where you can select which interface to serve to? It should be set to 192.x.x.x instead of "localhost" so that not just the local computer has access to it.
If you have antivirus that comes with firewall software, port 80 will have to be opened for incoming traffic in the third party software instead of the windows firewall. No more than one firewall should be active at a time, so if two are enabled, disable one of them.
Some firewalls have priority based rules so that rules at the top of the list override rules at the bottom of the list. You can try putting the rule to open up port 80 at the top of the list.
Make sure you can ping the apache server from another computer.
try telneting to the apache server on port 80
telnet 192.x.x.x 80
If it says "could not open connection to the host" then your server might still be blocking the connection. If the screen goes blank, then its good and pressing ctrl-c and enter might show you some stuff like this:
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">