Find out whether your existing apps are compatible with Windows XP with Service Pack 2 (SP2). The Application Compatibility Toolkit (ACT) 4.1 was designed to help minimize the risks associated with changes to the operating system and to deploy Windows XP SP2 quickly. Check out the excellent launch page that includes some handy associated links and tools, like VPC, Virtual Server, the AppVerifier, and TechNet's #1 most handy resource you should know about if you don't already - the Script Center.