I had similar problems following a clean re-install of XP Pro and SP3. Nothing I did could get the automatic udates to work so I went to the Microsoft Update site and they all installed manually without any problems. I then discovered a little utility on this site called "Dial a fix for Microsoft Dowmload problems" downloaded it and ran it. God knows how it works but immediately afterwards everything worked 100% and has continued to do do for some weeks now. Regarding Silverlight it could well be a completely different problem altogether as apparently several CPU's do not support Silverlight. My AMD chip doesn't but they don't tell you this on the automatic update as it just shows an error code. If you try downloading Silverlight direct from the site when you install it, it will then tell you what the problem is.