Microsoft Knowledge Base Article 315418 contains the following summary:
This article describes how to optimize and configure Group
Policy to increase logon performance.
When you start a Windows
2000-based computer that is a member of a domain, group policy settings from
the "Computer Settings" section of linked Group Policy objects (GPOs) are
processed and applied to the computer. Additionally, when you log on to the
domain, all group policy settings from the "User Configuration" sections of
each linked GPO are processed and applied. Because Windows takes time to apply
each policy setting, policy settings may slow the logon process, which can
result in a delay from the time that you start the computer to the time that
you are able to use the computer. This article describes methods that you can
use to minimize this delay.
