Windows XP SP3 Release Candidate – How to get it via Windows Update
If you’re a sysadmin for a small shop and are letting desktops update on their own, or if you’re at home and running XP, you may be wondering how to get SP3 Release Candidate to come down the pipe through Windows Update. It turns out that you need to flip a registry bit to get Windows Update to recognize that it needs to download and install it.
Microsoft has created a small utility to do this for you.
Windows XP Service Pack 3 Release Candidate 2 via Windows Update