Look in the system tray – if there's a connection icon of two computers? If not, then it is possible that the network card on your computer just disabled. To enable, open "start" - "control Panel" - "Network connections". In the opened window find "local area Connection". In the column "Status" will indicate its status. If the device is disconnected, click it, right-click and select the context menu item "Insert".
The situation is complicated if the list of network connections is empty. In this case, you need to check for a faulty network card. Open in control Panel "System" - "Hardware" - "device Manager". Look under "Network adapters". Most likely, you will see a device marked with a yellow question mark or exclamation mark. This means that the device driver is not installed or it is not working properly.
To network card started to work, you need to find her a driver. But you first need to know its exact name. If you know him, search the driver via Google search or any other search engine. If not, you will need the program Aida64 (Everest). Start it on the right side select "Computer" - "summary information" - "Network" and view the name of the network adapter.
Finding the network right driver, click "start" - "control Panel" - "System" - "Hardware" - "device Manager" - "Network adapters" and double-click the mouse marked with a yellow icon network card. In the opened window select "Driver" - "Update". As a source, specify the saved driver on your computer.
It is possible that the computer doesn't see network card. The reasons can be three: improper installation of the card, incorrect BIOS setting and notthe condition of most cards. In the first case, disabling the computer from the network, check the insert card in the slot. In the second, enter the BIOS and check whether network card. The third option is the most difficult, at home to check for a faulty network card can only be installing it on another computer.