Top fella Noel
Xmas hamper is in the post.
I changed the security settings like you said and got the dialog box back up but was still having to download files.
I've now uninstalled Quicktime and that's done the trick
I think I know what's happened. I downloaded iTunes the other night and this automatically installs a new version of Quicktime. This has then taken over my PC even though all the settings say otherwise.
Cheers again
Leon