Microsoft has made the Group Policy Verification Tool, Gpotool.exe, available for free download.
"This command-line tool allows you to check the health of the Group Policy objects on domain controllers.
Check Group Policy object consistency. The tool reads mandatory and optional directory services properties (version, friendly name, extension globally unique identifiers (GUIDs) and SYSVOL data (Gpt.ini), compares directory services and SYSVOL version numbers, and performs other consistency checks. Functionality version must be 2 and user/computer version must be greater than 0 if the extensions property contains any GUID.
Check Group Policy object replication. It reads the Group Policy object instances from each domain controller and compares them (selected GPC properties and full recursive compare for GPT).
Display information about a particular Group Policy object, including properties that can't be accessed through the Group Policy snap-in such as functionality version and extension GUIDs.
Browse Group Policy objects. A command-line option can search policies based on friendly name or GUID. A partial match is also supported for both name and GUID.
Preferred domain controllers. By default, all available domain controllers in the domain will be used; this can be overwritten with the supplied list of domain controllers from the command line.
Provide cross-domain support. A command-line option is available for checking policies in different domains.
Run in verbose mode. If all policies are fine, the tool displays a validation message; in case of errors, information about corrupted policies is printed. A command-line option can turn on verbose information about each policy being processed."