Vista lost network connection

My wireless Vista laptop no longer can access me desktop XP computer. Both can get on the internet going thru a linksys router. I am not sure why it lost connection been running for three years without problem.

The XP can access the vista folders, but when I click on the XP icon from the Vista I get a invalid host name. I am running Comodo firewall on both computer. What I would like help with is how do I check to see if the XP is a trusted computer on the vista firewall? I am not sure how to go about checking to make sure it has access to the XP. Thanks.