New Intrusion Attempts

I have never seen any intrusion attempts being blocked by the firewall until I changed something last night. I have two computers hooked to a router. The one has XP and Comodo Firewall, the other one has Vista and just the Vista firewall. I noticed that they were not set to use the same workgroup so I changed the XP machine’s workgroup from MSHOME to WORKGROUP, which was the one the Vista machine listed. Ever since then my firewall has been blocking incoming ICMP requests from the Vista machine with the source port given as Type(8) and the destination port of Code(0). I googled and it looks like these are ping requests from the Vista machine to the XP one. I never saw those before. I also got an alert for an incoming UDP request from the Vista machine to the XP one on port 137 which I at first blocked but after reading some things have now allowed.

File and printer sharing is turned off on both machines.

Are these things normal and should I allow or block them?

Requests on port 137 are normal as long as netbios over tcp/ip is allowed.

They should of course be blocked for wan.

If you don’t want port 137 requests for lan (but why, if you make a proper lan only rule?) you have to disable netbios, but then, each computer shall not “see” each other unless you choose another protocol.