I had that setting once at the office and I found it confusing but many people like it.
Here is a link about how to do it:
http://www.microsoft.com/windowsxp/u.../monitors.mspx
If you use an Acer computer, you can use the Acer GridVista software. If not, Ultramon seems fine:
http://www.realtimesoft.com/ultramon
Good luck
Olly