This post over at the Net 4 Nowt forum explains how to remove the annoying bar.

What you need to do is open Registry Editor (Start -> Run -> regedit.exe), navigate to HKEY_CURRENT_USER/Identities/{..}/Software/Microsoft/Outlook Express/5.0 and delete the key named BodyBarPath.

If you want to remove the “…provided by Wanadoo” text in the status bar, also delete the WindowTitle key.

Then restart Outlook Express and you’re done.