Wireless Connectivity

[#1]

Setup the router today (the broadband was activated last night) and connected the main desktop via cable and two laptops through wireless. Now here's the issue the one laptop, Windows 7 has been working fine with Wireless since being connected to it. The other laptop, a Dell inspiron 6400 with XP, has been problematic. It seemed fine to start with, being used upstairs, then the connectivity started dropping out. It would work for so long, then the wireless indicator showed that it wasn't recieving a wireless signal, it would then come back either by itself or by clicking on the symbol. After having it do that several times I thought I'd try it downstairs, pretty much next to the router but just as I was staring this post it dropped out. Now on a cable and its fine.
So any ideas why thi may occur? Could it be as simple as the Dell Laptop being a fair few years old?

[#2]

Also if you have a router dwnstairs how can you cable it to the upstairs?

[#3]

If your Dell laptop is a few years old there might be a bit of a problem connecting to the router whilst its set in its default wireless N configuration.
I would reccomend following this guide and in step two, change the broadcast mode from B/G/N to B/G and that should solve the problem. 

[#4]

Thanks for that