Take advantage of speed increases for Microsoft Outlook by upgrading to Service Pack 2.
“Office 2007 aggregates all of the security and other updates Microsoft has delivered through February 2009, but it also provides some interesting new capabilities. These include significant improvements to the stability, performance, and interoperability of the Office suite. That latter bit refers to compatibility with non-Microsoft file formats like PDF and ODF, the Open Document Format. Some of the biggest performance improvements are in Microsoft Outlook: Microsoft reports that that application is 26 percent faster than its predecessor on a set of common e-mail tasks and is even faster, at 35 percent, with larger mailboxes.”