Desktop real estate is a valuable resource on a computer, but sometimes one monitor simply does not provide enough space. A second monitor can cost hundreds of dollars, and not all computers are capable of supporting more than one screen. A spare laptop, however, can be connected to a host PC over a network to function as a second screen and increase productivity.

Hardware Issues

Laptop screens use different drivers and power settings than computer monitors and will not function without being connected to the laptop. A laptop screen cannot be converted into a stand-alone computer monitor; it needs to be connected to a working laptop. In order to use your laptop as a second screen, both the laptop and the host PC must be connected to the same computer network. The network can be a LAN or a WLAN, but if the computers are not on the same network, the host PC will not be able to use the laptop as a second screen.

MaxiVista's Capabilities

MaxiVista allows you to connect a laptop to any PC for use as a second monitor and can be used on computers running Microsoft Windows. With MaxiVista, you can drag windows from one screen to another and move the mouse from screen to screen just like a dual-display setup. The standard version of MaxiVista allows you to connect one laptop as a second display; the professional version allows you to connect up to four additional computers.

Using MaxiVista

Install and run the server application on the host PC and the viewer application on your laptop. Click on the MaxiVista tray icon on the host PC and select "Activate Secondary Screen" to extend your desktop to the laptop's screen. You can adjust where the second monitor is positioned by selecting "Monitor Position" from the same menu.

Synergy's Capabilities

Synergy lets you control two or more computers with one keyboard and mouse by moving the cursor across screens; it can be installed on computers running any operating system. Synergy does not expand the host computer's desktop onto your laptop screen like MaxiVista does; that means windows cannot be moved across screens. Both computers run their own applications, which allows you to maximize your computing power, and you can copy and paste data from one machine to another.

Using Synergy

Install and run Synergy on both the host PC and laptop. On the host PC, select "Server" mode, then configure the position of the laptop screen by clicking "Configure." A link will send the mouse to another screen. At least one link is needed on each display to move the mouse back and forth between screens. Add your links, then click "OK" and "Start." On your laptop, select "Client" mode and enter the name of the host PC. Click "Start" and your laptop will connect to the host, allowing you to scroll between computer screens with ease.

Source:

MaxiVista

Synergy

I think you can do this by 2 computers connected to the internet with different IP address. On the laptop you go into Start > programs > acsessories > remote desktop connection This should work for you. Check the http://www.computerspclaptop.com/category/tips-tricks for more laptop and computer tips