The use of more than two monitors with a virtual machine has certain limitations.
If you attempt to use more than two monitors with a virtual machine, your virtual machine must support more than two monitors for this feature to function.
More than two monitors is supported on Windows and Linux host and guest operating systems.
Windows XP guests support more than three monitors. However, only three monitors can be in use by a Windows XP guest at one time. If more than three monitors are connected to a Windows XP guest, use the Cycle multiple monitors button to cycle through the monitors to the configuration you want to use.