On two Windows XP machines of mine, the installation of post-SP3 patches has broken Windows Update.
I first wrote about this yesterday, when it happened on one machine. Today, on a computer with very different hardware, the problem repeated itself.
In both cases the computers had no application software installed. Each had only Windows XP SP2 and a handful of vendor installed utilities. Neither machine had any anti-malware software of any kind, not even a firewall (other than XP's firewall). Both were running Internet Explorer 6.
Each time I started by installing SP3 and rebooting. Next, I ran Windows Update manually and opted to install all the post-SP3 patches, with the exception of Internet Explorer 7. I prefer to install IE7 by itself. The patches install fine, and I reboot again.
At this point Windows Update no longer works.
As I suggested three months ago, it's best to hold off on Service Pack 3.
One Windows XP test machine started out with no service packs. I installed SP2, rebooted, installed IE7, rebooted, installed SP3, rebooted and then installed all the post-SP3 patches except for one. One patch had to be omitted because without something to install there is no way to know that Windows Update is broken. Specifically, I chose not to install KB923789, an update to the Adobe Flash player. The post-SP3 patches that I did install were KB951748, KB951978, KB890830, KB951376, KB950762, KB950760 and KB942763. One of them broke Windows Update.