If the network card is enabled, and there is still no joy, try uninstalling the device driver from within Device Manager. Reboot the system to reinstall the driver anew.
WARNING: Take note of the driver/software that will be uninstalled. Gather the necessary drivers from either the website that hosts support for your particular machine, or the device manufacturer website: Just in case Windows cannot find the proper software.
If the make/model of the machine and network interface card is provided, I'd be glad to lend a hand.
EDIT: Click Start
> type network connections
Please post a screenshot.