Lan wire plug turns off when i turn computer on

[doya]

I've got a used computer, has windows xp, says fujitsusiemenscomputers: I'm trying to connect it with a LAN cable to my broadband, when to computer is turned off, the light on the LAN cable plug on the computer is on, also the light for ethernet on my wireless box is on, when i turn the computer on, both of them switch off while the computer starts running. so the internet doesn't work then.
what can be done?

[Computer_Commando]

After the computer boots, do the lights come on?

[doya]

sorry, solved it already, it was the firewall..
thanx

xxx