PC freezes when networked with Windows XP PC

I support a small business which has two offices (one with 2 PC's and the
other with 3) each equipped with ADSL which is accessed via a router/hub.

The first of these has been installed a while and they have had an ongoing
problem with the Windows Me machine freezing when any application is used.
It was thought by the previous IT Support that this may have been down to
the Network Card and this was replaced. Apparently the machine worked fine
for a period until the problem manifested itself again. I have now
reformatted the machine and installed Windows 2000 Pro to see if the problem
can be solved. When this was done on my own network this configuration
worked without problem though we have yet to check this on the customers
network.

I have now come across the same problem at the business's second location
where a new ADSL router was installed and a second PC running XP was
attached. Whereas previously the Windows Me PC worked faultlessly, now it
is networked with the XP PC via the router it has the same problem as the Me
PC in the first office. When the XP PC is not switched on however the Me PC
works fine.

When the PC freezes the only option is to power cycle with a resultant
check-disk on boot-up which is totally inconvenient for the customer.

Any ideas folks?

Many thanks