PC doesn't recognize IP but does Localhost

hello all wise people out there that can help me
I have a situation

I have an apple mac, and a PC (OMG) connected both to a network.
the mac has apache up and running. i tried http://mac_ip/ on the pc and worked just fine.

the pc on the other hand has iis up and running too, but troubleshooting.
locally, on the pc, http://localhost works fine, but http://pc_ip doesn't.
just as http://pc_ip doesn't work on the mac.

note: the IPs are correct.

furthermore, i check the IIS configurations in control panel. The default web site is active, but the "IP Address" element in it's properties was set to "not assigned", so i chenged this to the pc's IP. I tried again, locally, and neither http://localhost nor http://pc_ip worked.
I reset IP Address to none, and localhost worked fine. but then agina, http://pc_ip didn't.

PLEASE
i'm desperate.


HELP
thank you VERY much to all those kind wise people who read this and might have a clue on what's wrong (and for those who don't, thnx 4 reading too)

I'd look for a firewall somewhere blocking traffic.

hey thanks but... firewalls??? you got me there! what am i supposed to look for? where? and how?

:$

Something that is blocking port 80 from some other computer to your webserver.

Since your web works properly from the webserver computer itself via localhost, then IIS is working properly. The only reason a request from some other computer would not work is if there is a firewall blocking http traffic from getting to/from the webserver to the remote computer.