If you have two or more computers in the same physical space that you want to control with a single mouse/keyboard you need "KM switch software".
I've tried three products
- Kavoom KM -- Very Solid product. Windows only. Unfortunately it is $39.95
- Synergy -- Cross platform (Windows/Linux/Mac), free and open source, but unfortunately the least capable of the three (as tends to happen with things cross platform).
- Input Director -- My current choice. Nearly as good as Kavoom. Windows only. Free.