Good answer Mattwray. This could work, although hardware profiles are designed to load specific drivers per profile.
It is worth a try. I still think two nics is the only way. I would like to know if the profile works.
To create a hardware profile
In Control Panel, double-click System, and then click the Hardware tab. Click Hardware Profiles button.
Click the name of the hardware profile on which you want to base the new hardware profile, and then click Copy.
Type a name for the hardware profile you are creating.
Change the hardware which is enabled or disabled in this profile by using Device Manager, as described in the following procedure.
To enable or disable hardware in a hardware profile
In Device Manager, expand the hardware type, and then double-click the hardware.
In the Device Usage box, clear or select Disable in this hardware profile.
Click Yes if you are prompted to restart your computer.
To delete or rename a hardware profile
In Control Panel, double-click System, and then click the Hardware tab. Click Hardware Profiles button.
Click the name of the hardware profile that you want to change.
If you want to remove this profile, click Delete.