If you move a computer or user between sites, domains, or OUs, or change its security group
membership, the GPOs scoped to that user or computer change and, therefore, the RSOP
for the computer or user is different. RSOP also changes if slow link or loopback processing
occurs or if there is a change to a system characteristic that is targeted by a WMI filter.
Before you make any of these changes, you should evaluate the potential impact to the
RSOP of the user or computer. The Group Policy Results Wizard can perform RSOP analysis
only on what has actually happened. To predict the future and to perform what-if analyses,
you can use the Group Policy Modeling Wizard.
To perform Group Policy modeling, right-click the Group Policy Modeling node in the Group Policy Management console tree, click Group Policy Modeling Wizard, and then perform the steps in the wizard.

Modeling is performed by conducting a simulation on a domain controller, so you are first asked to select a domain controller that is running Windows Server 2003 or later. You do not need to be logged on locally to the domain controller, but the modeling request will be performed on the domain controller. You are then asked to specify the settings for the simulation:
– Select a user or computer object to evaluate, or specify the OU, site, or domain to evaluate.
– Choose whether slow link processing should be simulated.
– Specify whether to simulate loopback processing and, if so, choose Replace or Merge mode.
– Select a site to simulate.
– Select security groups for the user and the computer.
– Choose which WMI filters to apply in the simulation of user and computer policy processing.
When you have specified the settings for the simulation, you receive a report that is very similar to the Group Policy Results report discussed earlier. The Summary tab shows which GPOs will be processed, and the Settings tab displays the policy settings that will be applied to the user or computer. You can save this report by right-clicking it and choosing Save Report.