You can sometimes have some conflit on listenning port and need find which application listen on it.
Skype or TeamViewer list both on port 80 and you may need it for IIS or another webserver program.
If you don't find which program is listenning, the easier solution is to use TCPVIEW, you can download it here :
http://technet.microsoft.com/en-us/sysinternals/bb897437.aspx
If one port is not avaible remotely, check Windows Firewall. We don't filter any port.