1 NIC with 2 networks

Each network interface can only attach to a single network at a time.

192.168.42.x seems like you're using the phone as a wifi/usb modem, can it be?
If so, the phone itself will become a second NIC with its own configuration and IP address, thus the computer will be part of 2 networks.

If the phone is using your wifi connection then it will get whatever IP address the DHCP assigns to it.
The 192.168.42.XX range is typically used by the phone internal DHCP server when it functions as a router (wifi/usb) for sharing its own internet connection.

Other than that I don't understand what do you mean by "tagged on the switch" or how exactly is your configuration.

Alejandro85 said:

Other than that I don't understand what do you mean by "tagged on the switch" or how exactly is your configuration.

That's HP Procurve switch configuration and tagged is the equivalent of a trunk port on a Cisco switch. The way that the port is set up is with a tagged port in one vlan for voice traffic and an untagged port in another vlan for the data traffic. Then the connection goes from the datapoint (connection to the switch) to the VOIP phone and from there to the PC.

I don't think that the PC will be able to see the tagged traffic this will not be routed on by the phone and the PC will be expecting to see it's connection on an untagged port but I could be wrong as it is not my area of expertise.

The answer is no, but you can set a static route in Windows so you can use your phone configuration software. I believe this will help... Static Routes - Create or Remove