Basically the router/modem is on the ground floor in an extension at the other side of the house. As a result, though I get a connection, its not that great, and the xbox will drop out of live making it pointless.

Ive been wondering about relocating the router to a central location on the ground floor so the signal covers the house better. This would mean making the parents computer wireless, as they wont let me run an ethernet cable under the floor. Obviously the simplest options are PCI or USB wifi adapters.

Im just wondering whether I can use an old router as a bridge or whatever theyre called, connect the parents computer to that via ethernet, and have that wirelessly connect to the router? Then I save £20+ on an adaptor. I dont know the technical jargon for what thats called, and whether it is possible.

Tech wise we have a netgear DGND3300 Rangemax affair at the moment, but we also have a DG834 router or two kicking around I think too?

You can bridge them easily. I have a seperate wireless AP that I have wired to my switch/router. If it is a wireless router that youyou have there should be an option somewhere to put it into a bridge/access point mode.