How to help Microsoft improve Group Policy and other aspects of Windows Server System platforms.
How to use the GPMC for auditing purposes.
Windows XP includes a handy tool called Network Diagnostics which can be used to gather a variety of information which can be helpful for troubleshooting.
A smart user who has local Administrator or Power Users privileges on their desktop computer may be able to circumvent Group Policy.
Check out the work of the Group Policy Task Force.