Netgear problem

I have a Netgear wireless router that has connected to my existing lap
top for ages without a problem. I tried to connect my works Dell D600
laptop the other day but I could not connect. I have tried wireless
and physical connection but I never get an IP address from my router.
The dell can see my network and says connected but then the connection
says limited or no connectivity. I have tried Netgear support but they
were rubbish! Anyone got any ideas?

I have connected to other wireless networks in the past so I don't
think the laptop is faulty!

I have previously had a similar problem with another Netgear router
where it would not connect to PC's using Belkin network cards, I know
this was fixed by changing a setting on the router (can't remember what
though and it may be something completely unrelated anyway).