yeah, just buy a wired X360 controller, plug it in, and XP (and Vista too, i'd assume) will automatically DL and install the necessary drivers. then its just up to you to configure it in the game controllers section of the control panel.
Yep fairly common and you can use multiple controllers on 1 adaptor I did it this way 'cos my son already had 3 xbox controllers and therefore it was cheaper than buying a new pc game pad. I got one for about £10 2nd hand on ebay about 6 months ago. Bosh £10 3 decent gamepads for my PC.
Do not know where you are in the world but here is a link for a simple search on PC, xbox, wireless receiver done on ebay.co.uk