outlook express

[Dzvid]

My OE no longer lets me delete messages in the ordinary
way - but I have found I can move messages to a new
folder, say x, then delte the folder, which moves to the
DElete folder and I can then delete that folder, still
called x, but I get a message which says "Folder cannot be
displayed - Outlook Express could not open this folder.
Possible causes are:

Low disk space.
Low memory"

But I don't appear to have low disk space or memory - I
still have 1 gigabyte out of 4 gigabytes left.

Suggestions welcomed.

Thanks

David