The Office team has released a patch so that Personal Archives and Exchange Online Archives can now also be used in Outlook 2007. The update is part of the "Office 2007 cumulative update for February 2011". The whole package can be downloaded here:
http://support.microsoft.com/hotfix/KBHotfix.aspx?kbnum=2475891&kbln=en-us
Details on Outlook 2007 and Exchange Archive can be found here:
http://msexchangeteam.com/archive/2010/12/20/457238.aspx
