Do you have two PC's, or a PC and Laptop standing on your desk? Then you probably have two keyboards and two mice, this can be very annoying if you have a small desk. But there is a solution called Synergy. With Synergy you can control two or more computers(Windows, Mac and Linux) with just one mouse and one keyboard. The setup is very simple, although I did need to make an exception in my firewall because it was blocking the program.
Oh, and the best part is that it's opensource and free!
You can download the program here: http://synergy-foss.org/
You could always check YouTube if you need help with the setup, there are plenty of tutorials.