If you have a system configured for Xinerama, you can easily adjust the XFree configuration file so you can use it for multiple users.

This will allow you to easily switch between a multi-user environment and a Xinerama multi-monitor environment.

What is Xinerama and how does the system configured using this HOWTO differ from a system using the Xinerama extensions in XFree?

The Xinerama extensions were introduced to the XFree86 system in version 4.0. Xinerama is an extension to XFree86 Release 6 Version 4.0 (X4.0) which allows applications and window managers to use the two (or more) physical displays as one large virtual display. In case Xinerama is not used, applications can only reside on one of the displays and can not be moved between the two. Window managers had to be specially written to support the two displays. With Xinerama, window managers and applications don't have to be specially written to support the larger “Virtual Desktop” Xinerama creates.

Just the opposite, the primary goal of a system configured according to this HOWTO is to offer multiple independent displays for several users on a single PC system.

For more information on Xinerama read: