hi everyone, havent been here in a while to ask any of my stupid questions

sorry if this is in the wrong board, couldnt find a network one.
i will add system specs if need be but im not sure if it will help.
So ive set up a wireless network. i am using a wireless router which has got my pc with winXP and an internet connection plugged into it, this is working fine.
i have connected my laptop with windows vista using a wireless network card and this is working fine including internet access through the pc.
then i connected another laptop with winXP using a wireless network card, it has connected to the network but will not let me use the internet connection on the pc, i know its connected to the network because i have played a couple of network games, ive tried re-installing internet explorer but there was no change.
is there any simple explanation, something that i have missed or didnt know about??