You'll need a wireless router and a PCMCIA card OR usb dongle (unless your lappy already has wireless on it)for the laptop. Think I saw PC World (booo hisss but its an example) doing an easter special in the ad in News of the World this afternoon. Should cost around £50-£60 for the lot.

Once setup you can setup a home network and access your desktop files with your wireless laptop

I have a Linksys wireless router and cannot fault it.

HTH

Andy