The first step is diagnosing the problem. So far your post doesn't provide much in the way of diagnostic info, but the first step is to ensure that both machines (i.e. yours and theirs) can see each other, this is done by pinging them. Note that Windows Firewall by default blocks ICMP ping, so you need to manually enable it. I won't describe how to enable ICMP ping in this post, but you can easily find it on the web.
Make sure your computer's name is resolvable from the other machine - if it's a NetBIOS name and your network doesn't have DNS registration for machine names then this might be a culprit - I personally find the NetBIOS experience in Windows to be very lacking, I don't know why we don't have anything like Apple's Bonjour/mDNS service. Use a command like
nslookup or even
ping to ensure the name is being resolved fine.
We've already established that you've disabled your local Windows Firewall, so that can be removed from the problem-space.
After you've established the machines can see and talk to each other, look at your IIS configuration and see what the bindings of the website are (open IIS, select the website, and click on "Bindings" on the right side of the screen). Ensure that it's bound to
0.0.0.0 (aka "All unassigned IP addresses") and that there aren't any other sites bound to your machine's address.
If that doesn't work, then we can't help you more without more information from you, like specific error messages.