For instance, if your colleague sends you a Powerpoint presentation, you can view the slides right inside Outlook 2007. And you don't have to install Microsoft Powerpoint on the computer, not even the free Powerpoint viewer.
Attachment Previewers for most common Office Applications, text documents and image files are pre-installed with Office 2007 while additional file previewers may be downloaded from the Office Online website. And like Outlook 2003, you can always double click the email attachment to open it inside the associated application.
If there are multiple attachments in an email message, say a HTML webpage and jpeg image, they will display in separate preview pane but in the same message window. Outlook file previewers also let you navigate inside documents and presentations that extend to more than one page.
Will save lot of time since you no longer have to wait for bulky Adobe Reader to load before you can view the contents of that 10 Kb PDF attachment.
Related: Create, Edit & Save Office 2007 Documents in Office 2003
Quick Note: These file previewers also allow you to preview files in Windows Explorer on Microsoft Windows Vista. If you are not using Office 2007, you may enjoy similar feature with X1 Desktop Search tool - X1 comes with even more file previewers like Adobe Illustrator and CAD file. Detailed Review of X1.