Did you get the control panel before you installed the network card drivers?
installing new drivers sometimes adds icons to your control panel for configuring the new device.
Sometimes the .CPL file associated with the icon causes problems with opening the control panel. I don't know why, but it just does. If you can find the .CPL file associated with the new network card you installed, then rename it or move it to a different directory. That should solve your no control panel problem.
Same thing happened to a friend of mine, and we moved the .cpl file to the same directory as the configuration .exe file for the network card he was using. He got his control panel back, and he was still able to use the .exe file to configure his network card.