My work setup is something like this – I have two desktop computers, each running Windows, and they are both connected over LAN. Each of these machines have separate monitors but they share the same wireless keyboard and mouse – thus the desk looks less cluttered and I can quickly switch between the two computers.

This can be done is multiple ways. There’s a simple hardware device called the KVM switch that is helpful when your computers aren’t connected over a network. With a KVM Switch, you can easily manage multiple computers (CPUs) with just one monitor, keyboard, and mouse.

The idea is a simple. The switch has USB ports where you may attach the shared keyboard and mouse. Then connect the switch and your computers using the included cables and you are good to go. Most switches have a button to help you flip between computers.

KVM Switch

KVM switches even make it possible for you share the same set of microphones and speakers with multiple computers. And it doesn’t matter whether your computers are running Windows, Mac or a mix of both.

Software Alternatives to KVM Switches

If you are not too keen on a hardware based solution and if your systems are connected with each other over LAN, all you need is copy of Input Director, a Windows-only utility that’s easy to configure and is absolutely free for personal use.

As a first step, you need to install the Input Director software on all your machines. The computer that is physically connected to the keyboard and mouse becomes the “Master” machine while other systems will be known as “Slave” machines.

The good thing about using a software based solution is that you can seamlessly switch between computers without having to press any buttons as in the case of KVM switches.

Update: See another good alternative to help you control two computers with a single keyboard and mouse
There are however a few points you need to remember:

1. Never shut down the Master machines without turning off the Slave machine first because then you would lose access to the keyboard and the mouse as well.

2. Don’t disable networking in Windows while the keyboard /mouse is active on the Slave side else you’ll have to restart the Master to regain control over the mouse and keyboard.

3. There may be instances when your Master machine won’t be able to recognize the Slave(s). In that case, simple right-click the Input Director icon in the system tray and choose “Rescan Slave Systems.”

4. Unlike a VNC software, you can’t drag and drop windows from one computer to another. However, Input Director supports clipboard sharing so you can copy-paste URLs and other text across computers.

Also see: Connect Laptop to your TV

[*] Input Director is for Windows only but if you are work with both Mac and Windows, or if you intend to use the program in a commercial environment, check out Synergy.

[**] If you only want to share a monitor between two computers, you don’t even need a KVM switch. Just connect one computer to the monitor using a VGA cable and the other monitor using the DVI or HDMI cable. You can then switch between computer using a button on the monitor itself.