how to use multiple display with one computer

MaxiVista turns any networked computer into an external monitor. MaxiVista's only
hardware requirement is that the two computers must connect to each
other across a network, so it's perfect if you can't add an extra video
adapter. I have a network adapter for my old laptop, so I connected it
to my network and installed the free MaxiVista demo. It worked and my
laptop's desktop was immediately spread across three displays, as shown
in Figure 1.

Figure 1: MaxiVista at work.

If
you don't have an old laptop lying around, you can buy a used laptop
for cheaper than an external monitor would cost. It doesn't need to be
fast—even very old hardware will work with MaxiVista.

Configure MaxiVista

To configure the MaxiVista demo, follow these steps:

1.	Connect your primary PC (the one to which you'll connect your keyboard and mouse) and your secondary PC (the one that will act as an extra monitor) to a network. If you don't have a network yet, connect the two computers with an Ethernet cross-over cable.
2.	Download MaxiVistaDemo.Zip and open the file in Windows Explorer.
3.	Run MaxiVista_Setup_PrimaryPC.exe on the primary PC and follow the wizard's instructions.
4.	Run MaxiVista_Setup_SecondaryPC.exe on the secondary PC and follow the wizard's instructions.
5.	Right-click the MaxiVista icon in the notification area and then click Enable Secondary Display.

MaxiVista
isn't quite as nice as having an external monitor directly attached to
my laptop, but it's close. I can't run any 3-D games on the MaxiVista
display nor can I watch DVDs on it. I can, however, keep my instant
messages, e-mail, Web browser, or word processor on the display. Though
it has its limitations, MaxVista gave me the desktop space I needed
without requiring me to buy any new hardware.

Ref :Tony Northrup