Dell optiplex gx620 won't let me access the internet via LAN

[Dedrix]

Hello, my Dell optiplex gx620 won't let me access the internet via LAN. does anyone know how to fix this?

 

[Emerald]

are the network card drivers installed?

do you get an IP from the router?

can you PING the router?

can you Ping www.yahoo.com?