As you may be aware, enhanced multi-monitor support was introduced in Hotfix Rollup Pack 1 for Citrix Presentation Server 4.5 and version 10.100 of the Presentation Server for Windows Client - so you should be at these revisions at least to benefit from this new functionality.

Citrix state that limited support is available for previous versions of Citrix Presentation Server and the Presentation Server for Windows Client but they recommend that if you are planning to use multi-monitor workstations to connect to published applications, you should dip into that SA license cost and upgrade to Citrix Presentation Server 4.5 Hotfix Rollup Pack 1 or later.

Citrix have released a KB article providing the available configuration settings that can be used to control specific multi-monitor functionality in a Citrix environment.

The snappily titled "Citrix Multi-monitor Configuration Settings and Reference" includes controlling the interaction and display of specified applications and application windows as well as ICA session behavior.

Under most circumstances, the default settings will suffice for the majority of applications. The additional settings described in the article allow you to have a more granular control over multi-monitor sessions that might be required with some custom applications and/or in some deployments.

To read more follow the link to  CTX115637 - Citrix Multi-monitor Configuration Settings and Reference