Hapy Easter etc.
Although I wasn't going to I couldn't resisit the temptation - downloaded build 7077 X-64 (thanks to Soligor and his Russian contacts). Download fine -- 90 mins approx -- plenty of seeders now.
Noticed though on Network Discovery I randomly See XP machines on the network but randomly don't see them either -- seems to be totally unpredictable when the machines are visible. (These machines are 100% logged on).
However there's absolutely no problem in "Manually connecting" using connect network drive and then specifying the actual UNC address such as via \\xpmachine_name\share_name
(Of course you have to know the share names if you connect like this. If you don't know the share name then you are totally screwed).
Doesn't matter whether Firewalls or on or off - same problem.
Machine is fine in build 7068 x-64. All networked (XP) machines always available
Looks like these later builds are doing things with Networks.