Here's an answer for those folk that have to manage PCs that are used in public locations and/or PCs with multiple user accounts.

Microsoft Shared Computer Toolkit for Windows XP.

http://www.microsoft.com/sharedaccess.

Shared computers are found in schools, libraries, Internet and gaming cafés, community centers, and other locations. Often, non-technical personnel are asked to manage shared computers in addition to their primary responsibilities.

Managing shared computers can be difficult, time-consuming, and expensive. Without restrictions, users can change the desktop appearance, reconfigure system settings, and introduce spyware, viruses, and other harmful programs. Repairing damaged shared computers costs significant time and effort.

User privacy is also an issue. Shared computers often use shared accounts that make Internet history, saved files, and cached Web pages available to subsequent users.

The Microsoft® Shared Computer Toolkit for Windows® XP provides a simple and effective way to defend shared computers from untrusted users and malicious software, safeguard system resources, and enhance and simplify the user experience. The Toolkit runs on genuine copies of Windows XP Professional, Windows XP Home Edition, and Windows XP Tablet PC Edition.

The Toolkit includes several command-line tools and the following graphical tools:

Getting Started. Provides access to computer settings and utilities and helps first-time operators learn the Toolkit basics quickly.
Windows Disk Protection. Protects the Windows partition (typically drive C) that contains the Windows operating system and other programs from being modified without administrator approval. Disk changes made are cleared with each restart unless the administrator chooses to save them.
Windows Restrictions. Restricts user access to programs, settings, and Start menu items. This tool also allows you to lock shared local user profiles to prevent permanent changes. (This tool is specifically for use in workgroup environments that do not use Active Directory and Group Policy.)
User Profiles. Creates and deletes user profiles. You can use this tool to create user profiles on alternative drives that will retain data and settings even though Windows Disk Protection is on. You can also use this tool to completely delete profiles that have been locked by the Windows Restrictions tool.
Accessibility. Makes Windows accessibility options and utilities such as StickyKeys, FilterKeys, and Magnifier available to users who have been restricted from accessing Control Panel and other system settings.