Stonie, are you running XP on the laptop? If so, click start and then run, type 'cmd' into the open box and click ok. This will bring up a black box. In there, type in 'ipconfig /all', it should give you the address of the Wireless LAN adapter, and also the default gateway which is your router. You don't want any I.P's being the same as that will cause a conflict and knock one device off the network. So what i suggest is write down your default gateway from here (usually 192.168.0.1 / 10.0.0.1).
Then go into Start > Control Panel > Network Connections. You should see a Local Area Connection that relates to the wireless lan adapter if its been installed correctly. Right click this icon and left click properties. Then you need to left click 'Internet Protocol (TCP/I.P)' and left click 'Properties'. In here, change the bullet point to 'Use the following address'. Put your I.P in very similar to the gateway you written down before but change the last set of numbers (i.e. 192.168.0.100). For subnet mask put '255.255.255.0' and for default gateway type in the default gateway number you written down before. Click 'Ok' and then restart the laptop, then try to browse the web when it comes on again.
If this does not work, undo the settings above and will have to try something else. Sorry that it's very technical what i've put, any problems pm me.