Windows 7 Network Adapter Code 12

This might be worth a read.....

http://technet.microsoft.com/en-us/library/cc732199(v=ws.10).aspx


and this.......
Code 12
This device cannot find enough free resources that it can use. If you want to use this device, you will need to disable one of the other devices on this system. (Code 12)
Cause

This error can occur if two devices that are installed on your computer have been assigned the same I/O ports, the same interrupt, or the same Direct Memory Access channel (either by the BIOS, the operating system, or both). This error message can also appear if the BIOS did not allocate enough resources to the device.

Recommended resolution

You can use the Troubleshooting Wizard in Device Manager to determine where the conflict is, and then disable the conflicting device.

Disable the conflicting device

1. On the device Properties dialog box, click the General tab.
2. Click Troubleshoot to start the Troubleshooting Wizard. The wizard asks you some simple questions and provides a solution to your problem based on the answers that you provide.
3. Follow the resolution steps provided by the wizard to resolve the problem.

Also...try using the card in a different PCI slot.