http://www.ieinfosite.co.uk/tip_view.asp?id=162

If the toolbar in Outlook express has gone missing, first of all try putting it back by right-clicking the menu and selecting Toolbar. If this doesn’t do the trick, you’ll need to make a small change to the registry. Start regedit (Start, Run.. and type in regedit) and browse your way to the following key:

HKEY_CURRENT_USER\Identities\{(whatever you have here)}\Software\Microsoft\Outlook Express\5.0

To get the main Outlook Express toolbar and menubar back, double-click the Browser Bands string in the right-hand pane and change the fifth number to anything other than 00. 01 and 02 appear to bring back the menu bar. 03 and 04 bring back the menu bar and toolbar.