You can share a printer with wireless. Can you search for the computer? Right-click on "My Network Places" on the desktop and choose "Search for computer". Type in the computer name and see if it finds it. That fact that it can ping is good, but if you cannot search for the computer definately is a firewall problem.

Personal Firewall Interferes with Windows Networking
http://www.practicallynetworked.com/...ewall_prob.htm