XP-AntiSpy is a little utility that let's you disable some built-in update and authetication 'features' in WindowsXP.  
For example, there's a service running in the background wich is called 'Automatic Updates'. I don't know what this service transfers from my machine to other machines on the internet, especially the MS ones. So I play it safe and disable such functions. If you like, you can even disable these function manually, by going through the System and checking or unchecking some checkboxes. This will take you approximately half an hour. But why wasting time when a little neat utility can do the same in 1 minute? This utility was successfully tested by lots of users, and was found to disable all the known 'Suspicious' Functions in WindowsXP