What a waste of time, effort and energy.
I refuse to allow automatic updates, for reasons we have discussed and mostly agreed on here in the past, but I do allow the notification of available updates, allowing me to choose which updates I wish to install.
Over recent months I have been constantly reminded (by constantly read several times daily) that I need to install a most "important" update in the form of a service pack to Windows XP. I have ignored this as I use Vista. In the past month I have also received many reminders that I need to install a service pack (1) to Vista. I said yes to that as it seemed to me to be a prudent move to install a service pack and iron out any bugs they had corrected. BUT it would not install. Always refuses to install telling me that it is "not compatible".
Yesterday they offered me Service Pack 2 for Vista. ~ Good plan I thought. So I clicked on install.

Naturally it will not install .... and the reason? because I do not have component parts of Service Pack 1 installed to enable Service Pack 2 to install.
Words with Microsoft via the telephone have been spoken. The geek was incredulous that there should be any difficulty ..... in fact he went so far as to suggest that perhaps I didn't know what I was doing. How much training does one need to click on "Install"?
Perhaps in revenge for my calling him a gormless twat my PC then dropped its internet connection giving me an error message saying that my "Ethernet Driver had ceased to function and had to be reinstalled".
Bollox!

~ I turned the damned thing off, waited 30 seconds and switched it back on .... It works again.