You can use an old laptop as a second screen. However, this process is different than setting up a standard second monitor on Windows 7. Since laptops don't have video adaptors, you need software to allow the screens to communicate over a network or Ethernet-wired connection. Make sure that both of your computers have access to your home network. If you don't have a home network, you can use an Ethernet crossover cable to link your two computers.
Make sure that both you main computer and laptop are connected to you home network. This can involve plugging them both into your router using a LAN or Ethernet cable, plugging wireless network adaptors into both, if you have a wireless router, or a combination of the two. Most modern laptops have a built in wireless network adaptor.
Use an Ethernet crossover cable if you don't have a home network. Plug one end into the Ethernet slot on the back of your computer and plug the other end into the slot on the back or side of your laptop.
Download software to send and receive information over your network which communicates the state of the desktop display. This involves downloading software to both your main computer, to send the information, as well as to your laptop to receive and interpret that data and produce an image. There are a range of options which can be downloaded (see Resources), depending on your requirements.
Install ScreenRecycler (see Resources) to use your laptop as a second monitor if you are using an Apple Mac computer. This program has been designed to work with the Apple operating system, but you can use either an Apple or Windows laptop as your second monitor. You can pay to download the latest edition of ScreenRecycler or you can download an old release for free. With the free software, you will more likely suffer a slight delay on your second screen. In addition, as of 2010, this program only supports the use of one extra screen.
Install either ZoneScreen or MaxiVista (see Resources) to use your laptop as a second monitor if you are using a Windows computer.
Zonescreen is free to download but is an old project which stopped being developed in 2003. This means that there can be a slight delay on the second monitor, especially when the computer is performing resource-heavy tasks, such as watching a video.
MaxiVista is much more advanced than ZoneScreen. The program will hardly ever suffer from any delay and offers a good resolution and screen refresh rate for using your second screen to watch videos. MaxiVista also supports using up to eight screens across four different computers or laptops.
Install Air Display to use your iPad, iPhone, or iPod touch as a second screen. This integrates many features of the original devices into the service. For example, you can rotate you iPad screen between its vertical and horizontal positions and the display will adjust to suit the new position. You can also use the touchscreen features to control the cursor on your second screen. Air Display works with both Apple and Windows computers.
Download the MaxiVista demo file (see Resources).
Double-click on "MaxiVista_Setup_PrimaryPC.exe" to install the program on your main computer.
Repeat step 1 on your laptop, or use a memory stick, floppy disk, or other method, to move the file "MaxiVista_Setup_SecondaryPC.exe" to your laptop.
Double-click on "MaxiVista_Setup_SecondaryPC.exe" to install the program on your laptop.
Double-click on the MaxiVista icon on your main computer's desktop to open the "Options" screen.
Click on "Enable Secondary Display" in the "Options" screen. Your laptop will now display as an extension of your main computer's desktop. To turn this feature off, click on "Disable Secondary Display."