Help! I can't get the internet on my laptop any more :(

Desktop PC – Sony Vaio PCV-W 1/G (running Windows XP)
Laptop – Sony Vaio VGN-NR10E (running Windows Vista)
Cisco cable modem 2100
Wireless router – Netgear WNR2000v2

I’ve recently changed my modem and router because our other wireless router was making a strange noise and the internet connection was very slow. Our ISP (Virgin Media) supplied us with a new router and modem, which we set up according to their instructions but for some reason, we can’t get the wireless to work on my laptop any more.

For some reason, when I try to connect to my wireless network via my laptop, I can only get limited connectivity but the internet works fine on my desktop computer. All the lights on my wireless router are on, indicating the connection is working fine.
When I try to connect directly through the Ethernet cable, again, I can only seem to get limited connectivity! It also describes my network as ‘Unidentified Network (my network name)’.
Please can you suggest some things to try because I really need my laptop to be able to use the internet, as I’m going to university soon and I don’t want the expense of having to buy a new laptop on top of everything else!
Thank you