[pptp-server] Default gateways...

[Mr Magoo]

I know this question has been asked before, but it doesn't seem to be in any
of the HOWTOs or FAQs.
	Once the windows box connects to the VPN, he has the default gateway of
that computer.  On my network, this also gives him internet access through
my gateway.  How can I create a route where 10.0.0.X traffic will be sent
over the tunnel, and all other traffic will go over their regulair line?