XP PRO IN WORKGROUP AND GUEST ACCOUNT

HI all,
Got a little question for you. I got 2 Xp pro machine in a single workgroup(ABCD). The 2 computers see each other in the network places. But when a try to see or connect a shared. I got an error telling me… It does not accept blank password etc. I can make it work is a unable the guest account but i dont want to. Is there a way to make them communicate without using the guest account. If I open the guest account and I’m behind a Linksys firewall/router. What is the possible security risk.