Well I still don't get any control over network discovery, but it seems like when you choose your IP manually, the shared option finds its way a little easier.
Goto System Preferences>Network , click on the device you use to connect to the internet (ie: Ethernet or AirPort)
In Configure IPv4, choose: "Using DHCP with manual address"
enter an IP address (which is in your router's scope, but outside its DHCP scope), subnet mask, router (default gateway) & DNS server. If your PC('s) is (are) under a domain, enter the domain name.
Make sure the IP you use is not used by any other device in your network. It will create a conflict.
CAUTION: I suggest to be familiar with TCP/IP configuration before you modify anything.
I hope this helps.
Message was edited by: iRaf