Ok, for anyone who doesn't know, this is actully a wired 360 controller - it connects to 360 via USB and it's compatible with windows and actually, very, very good for using with the PC. Microsoft knew this when they made it, that's why they made it connect via standard USB rather than it's own controller connection. Nice!
All those games for your PC like GTA IV or driving games and the like, where you think you would have preferred a console controller... this is it.
If, for some reason your windows doesn't recognise it properly, you can download a specific driver from Microsoft's website. Only compatible with Vista and XP (not 2000 as I once found)
Remember, it's a 360 controller... will work with PC and 360. If you have a 360 already, you can use the wired controller with the PC. If you need another controller for your 360, again, you can use this :)