Outlook Express question

[Sokartawi]

Someone else at work uses Outlook Express for email, but that program sometimes gives the nag message if it can compress emails to save disk space. Since this person is usually very busy, she sometimes accidentally clicks on OK which starts the process and makes old emails inaccessable, plus the process takes very long (we're talking about thousands of emails here).

There is a box that sais "Do not show this message again" but it keeps comming back anyway.

Any idea to crush this annoying nag message once and for all?