Problem with KMail 1.9.9

Hi! I am switching my husband from Thunderbird to KMail, as I would rather have him on KMail. But I have promised him that I will make it look as similar as possible to what he is used to, so that nothing that he does needs to be different. I know his way of working, and this is achievable. Except.... Except for my current problem. Yesterday I started to set KMail up, and made a few entries before I had to go. Today I switched off the favourite folders pane, went to carry on setting up where I left off - and noticed that there was no inbox. Obviously I can create a folder called Inbox, but it puts itself at the bottom of the default folders list with a standard folder icon, instead of at the top of them with the inbox icon. Furthermore, the few settings I entered yesterday have disappeared. :-( PEBKAC is a definite possibility, given that I haven't been well and am on a large dose of a strong antibiotic, but even if it is my fault, I still need to put it right. I have tried to purge and then install, but that seemed to intend to remove most of the desktop. So I ran aptitude reinstall. Nothing changed. I ran aptitude autoclean, aptitude reinstall, no joy. I then went on to Google. There was lots on disappearing emails, but nothing on disappearing folders. And that was after I had managed to get rid of most of the KDE4 stuff. So, help!! Thanks, Lisi