I am a network admin for a small company and am looking at a problem:
I need to find a solution for our employees connecting from different
locations around the world, to our company LAN, one way or another.

We have been using PPTP (as built-in in windows) thus far, but our
problem is that people sometimes make connections from subnets that
match our subnet (the "192.168.0.x problem") and we cannot really
afford to change either. I have read that setting up a VPN-like
solution trough IPSec would overcome the problem. Is this true?

I understand there are some issues like certificate deployment, but I
do not believe this could be a problem considering the point that all
company computers start their life in my office. I am not too eager to
go for any extra commercial solutions and am hoping to be able to use
what we already have (windows server ISA / windows XP workstations).

Can IPSec tunnels also be used to link LANs (two LANs filled with
workstations, same subnet, two machines used as gateways for N-way

Thanks for any help in advance.