I know what you mean, I loved working on computers until about 6 years ago. So I have a bit of knowledge but know sweet FA about wireless stuff lol. Might get the USB one, no taking anything apart would be a bonus lolSomething like this will get you a good result! You will need a spare PCI slot, double check this. If you have no idea what i'm talking about just say, lol.
http://www.amazon.co.uk/dp/B00008DOYL/?tag=cliospnet01-21
If not then something like this (USB)
http://www.google.co.uk/products/ca...B+wireless&cid=5763188691193284800&sa=title#phttp://www.amazon.co.uk/Linksys-Cisco-WMP54G-Wireless-G-Adapter/dp/B00008DOYL
How far away is the Desktop from the Wireless router, can't you connect it directly?