Internet Gateway in XP Pro

For the reasons of gaming, I need to enable the NIC on my machine for LAN gaming, and keep my WiFi for internet.

If I enable the WiFi and the NIC together XP Pro makes an Internet Gateway and the game crashes. But if I disable all but the WiFi (main Internet connection) the game runs fine. If I disable all but the NIC, I get the Gateway and the game crashes.

Is ther a way to stop XP from creating this gateway?