Make sure Client for Microsoft Networks, File and Printer Sharing for Microsoft Networks, Internet Protocoal (TCP/IP) are all installed under Local Area connection properties.

You can also try uninstalling the the network card drivers then reinstalling them. Make sure you have the driver for the NIC before uninstalling it.

Before all that, first check to make sure the NIC is getting a proper IP addres.

Start->run->cmd then click on the ok button.

next type in ipconfig
then press enter

If you are getting all 0s for IP then yeah you're not getting an IP.

I'm assuming you're using DHCP, so type ipconfig /release
then press enter.
Next type ipconfig /renew

I'm assuming you're using W2K or XP as the OS.