I just spent several hours (again – as I’d forgotten the last time) trying to get two XP boxes to talk at home. I use checkPoint VPN to remote into work and so typically use one machine at a time as they’re not grunty enough to use Virtual PC (anyway – that’s a different story).
I forgot that if I actually want to use ICS on the network (without nifty NAT setup – which I’m not capable of and bothered to learn), I have to disable CheckPoint VPN on the internal network adapter on the ICS host, and also on the client machine/s. If you don’t you’ll be ‘pinging in the wind’ to eternity wondering why the hell you can’t see the machine right next to you.
Hopefully this entry will prompt me the next time I run into the problem!