Im running dual boot WinXP and Ubuntu 6.1, with two network cards. One card goes to my college network, the other to my personal file server and laptop when its plugged in.

The second connection has no route to the internet.

Under Linux I have simply removed the entry in the routing table which trys to use eth1 for internet traffic and all is well.

Under windows I cant figure out how to do this and it keeps switching between adaptors. This causes the internet to only work ~50% of the time, which is very frustrating.

 Does anyone know how to tell WinXP Pro that it is not to use one of its available ethernet cards for internet traffic without disabling that card completely?

as DeltaZeros  mentioned, default route needs to be emtpy on the non internet adapter.

if it is, then run cmd from the start > run

then type route print
that will show you the routing table windows is using,
if theres an entry for 0.0.0.0 on both ips youve got, remove it from the non internet one and all should be well.

route del is the command but i cant remember the syntax from memory, just type in route and itll spit out the help documentation

ROUTE DELETE 0.0.0.0 IF x

Where X is the number of the interface from which you want to remove the route.