Have a Widows XP Pro desktop automatically getting updates from Server. Unable to install KB2633870. Associated Update KB2600217 installs ok. I have 50 other desktops and laptops where the update installed no problem. Tried repair of .net Framework 4. Tried Uninstalling and reinstalling .net Framework 4. Still no go. I don't want to reinstall Windows but I am prepared to do it as last resort.