obating internet acess and network on separate routes

Hi

We are trying to have internet service and our secured network available in
the workstations at the same time.

We can obtain it independently. Our setup is as follows
Windows server 2003 and Windows XP Pro. We have a network set up with its
own ip address and submask. This is a secured network. Then for internet and
our in house system it has its own ip and submask. We can only use 1 network
card in each workstation.

As I said we can access each independently, but the transition is slow and
at times we need to repair the connection. It like it doesn't switch domain
or very slow to switch. Then the operation is very slow

I thought there was a way to set the shortcuts for access through one path
and anther shortcut through another. For example set up the secured to use
one ip and submask and then for internet use the other ip and submask
Perhaps I am wrong. If this can be done would it cure my problem.

In any event we want to be able to have both programs operational and be
able to switch between the with alt tab a the same time.

Any suggestions and or question appreciated as I am sure I didn't explain it
as best needed

Thanks
Rick