Some more information that will help : Windows version, network card make and driver version. I will assume Windows 7.
Fully patch Windows
Call up Windows Update and install all updates, including optional ones.
Check network driver version
Find on the website of the manufacturer of the network card the latest driver
for the card (if available), download and install.
Check Windows integrity
Execute sfc /scannow
to check the integrity of all protected Windows 7 system files and replace damaged versions with the correct ones (if possible).
Verify TCP/IP Settings
In Control Panel -> Network and Sharing Center -> Change adapter settings, right-click
the network adapter and choose Properties.
If you don't use IPv6 in your home network, uncheck Internet Protocol Version 6.
Click on Internet Protocol Version 4 and then Properties, and
ensure that both the IP and DNS server addresses are set to automatic.
Run the Command Prompt (cmd) as Administrator and type
netsh int ip reset c:\resetlog.txt
and press Enter. Reboot.
If the above has not resolved the problem, try to see if it arrives when booting in Safe Mode with Network. If it does, then Windows is damaged and should be repaired.
If it does not arrive, then some installed product is responsible for the problem.
You might also consider rolling back to a system restore point dating from
before the problem occurred, if no other changes were made to Windows in that period
beside these of the network card (such as installation of new products).