Try this:
Click Start, run, then type: msinfo32
In the System Information window, click Components, Problem Devices.
Get the VEN # and the DEV # for the Network card
Goto http://www.pcidatabase.com/index.php and do a search for the VEN and DEV numbers.
This well tell you the manufacturer. Then goto the manufacturer's website and find the driver.
Then you can download DriverMax http://www.innovative-sol.com/drivermax/
It will search for drivers for you if you need other drivers for the system. It's a great utility.
If you still can't find the drivers with DriverMax, repeat the step above about the VEN and DEV numbers for each unknown device until you find what you need.