Thanks chaps
172.16.0.0-172.31.255.255 is one of the other IANA agreed blocks for private networks - I chose it because it was less obvious than the 192 block. Should be OK
AFAIK but I can try changing it.
Isn't it insecure to have the gateway on the same subnet? For M1 and M2 to see each other you's have to enable File and Printer Sharing which would leave you wide open on the Web!
I s'pose I could always disable F&P sharing on TCP/IP and enable it on IPX/SPX for M1/M2
I'll tinker some more but suspect that XP on M2 is hosed and may require reinstalling from scratch.
All suggestions welcome - thanks again