Network Niggle

I have a confusing little problem on my office network. We have a Netgear router and all ports are used in on network. One of the ports leads to a switch to serve two laptops, the problem I am having is that one of this laptops says that it is connected to the LAN but I cannot access the internet or anything at all. The second laptop connected to the switch works perfectly as my laptop does too if I plug it into the switch. I have had a look at the settings on the laptops and all seem to appear the same; ie automatically detect settings. I have tested the cable to the laptop in question and it is fine, when plugging in the other laptops it works fine. I have tried disabling the softwarre firewall too.

Has anyone any ideas what may be the problem or where to go from here?

Thankyou for your assistance :confused

OS is XP Home on the computer that does not work
Other computers running from the router are on XP Home and Vista. 2 of laptops that work on the same cable are XP home.

 

Can the laptop in question ping the router or other computers? (If you have no idea what that means, just say so and we'll explain)