Hi FF. Many thanks for your reply to my post.

I downloaded the Windows Installer Clean-up Utility to my desktop. But when I went to install it I was presented with a dialogue box headed ' Installer Information', which said: 'Error 1500. Another installation is in progress. You must complete that installation before continuing this one'.

Do you think this is related to 'Automatic Updates' which, when I shut down my computer, keeps trying to install a Service Pack for .NET Framework 2.0? The Service Pack seems to have downloaded OK but will not install.

Further, I notice that the 'Welcome' dialogue box for 'Windows Installer Clean Up Set-up' has an image with the words: 'Microsoft Office Update' Does this mean anything?

Thanks again for your welcome help, FF.