Windows XP originally shipped with the USB audio bug which caused some units to have clicks and pops. The solution was included in the "Microsoft Messenger" patch, but once this became part of the Windows XP Service Pack 1 (a collection of all current updates at a specific time), the USB bug was not fixed, and the Microsoft Messenger patch will not install because it is supposedly already installed. In one case, a customer installed Service Pack 2 Release Candidate 1 and solved the clicks and pops problem. Release Candidate 1 is a publicly-available pre-release of Service Pack 2, not guaranteed to be bug-free. It is available at www.microsoft.com