Microsoft Wireless Optical Desktop 5000

Beware of this product. Got intermittent warnings about a weak signal, even when the batteries were new and the keyboard and mouse was next to the receiver. I've since changed it for another without any problems.

Be careful with this keyboard, I am pretty sure there is a bug built in, if you don't let your windows updates download, the whole thing, mouse and keyboard start behaving very strangely, doing things that you don't ask it to do, I know its the mouse and keyboard, because after days of thinking my computer is bugged, I got rid of the wireless and plugged back in a wired keyboard and mouse, and no problems what so-ever. Just a warnings.

So all I can say is be careful what you buy.