Some laptops won't connect to LAN

This is a bit of a strange problem - for me anyway.

I have VirginMedia 2Mb broadband at home with their vanilla modem from which I run a cat5 cable to my desktop PC. That all works fine, has done since the day I plugged it in.
However, if I connect with the exact same cable to my laptop (IBM Lenovo Z61m) Internet doesn't work. This laptop I use on both wired and wireless networks elsewhere and never has a problem.

Similarly, my sister just bought a VAIO (will have to find out exact model) which was working fine on a wired connection at my parents' house, yet when she takes it home and connects it to a cable modem, again with a cat5 cable (similar configuration to mine) then that too doesn't work.

My house (wired only modem):
My desktop: Previously running XP Pro, now running Vista Ultimate - always works fine
My laptop: Running XP Pro - doesn't work (but works with all connections elsewhere)

Parents' house (wired and wireless ADSL router):
My laptop: running XP pro - works wired and wireless
Sister's laptop: running Vista Home Premium - works wired and wireless

Sister's house (wired only cable modem):
(Very) Old Compaq laptop: running XP Pro - works wired
Sister's laptop: running Vista Home Premium - doesn't work wired

Help?

 

Yeah, its a normal problem don't worry. The thing is, that your provider has saved the MAC address of you desktop PCs network card. It doesn't allow other MAC addresses to connect. If your provider allows more PCs on that connection, usually a call to them solves the problem. Just attach a vaio...or anything and call them that you need to unlock that MAC address.

Hope it helps

 

The best thing to do is spend £10-£20 for a cheap wired cable router and be done with it

 

Ah ok, thanks very much guys. I've never had cable before so bit of a noob in this area!