Wireless & LAN together

I am trying to connect a computer in our office to a Wireless Netgear Router using a Netgear USB dongle. At the same time, the computer is permenantly connected via Ethernet to our till systems. I have managed to install the wireless usb dongle without any problems and I am able to view the wireless network no problem. For some reason, I can't seem to access it.

I have tried to ping the router but it doesn't seem to work however, I can ping the two tills on the ethernet connection. It seems as though the computer is defaulting to ethernet rather than using the wireless connection.

Is it possible to use both connections side by side? I have tried so many times and am now pulling my hair out!

I have managed to connect other devices to the router without any problems and can access the internet with a 100% reliable, stable connection.

System Specs-

Windows XP Professional SP2
Netgear WG111T Dongle
Netgear DG834GT Wireless Router


Hopefully someone can help me! Many thanks!

gwyn_mon