Microsoft MSDN provides free Preview Handlers samples to preview the content of various types of files from within Outlook 2007 or Windows Vista Explorer Preview Pane without opening the file(via). After you install the package, you will be able to preview the content of following file types from Outlook 2007 or Vista Explorer Preview pane:

XPS Preview Handler: XPS is Microsoft’s alternative to Adobe’s PDF format. This plugin allows you to preview XPS files
MSI Preview Handler : Tells you the contents of the .MSI file, the size of each file and the version of each file by default.
CSV Preview Handler: Displays a .CSV file as if it were a spreadsheet.
ZIP Preview Handler: Besides showing the content of a ZIP file directly within the preview pane of Windows Explorer or Outlook, it will allow you to directly open any of the files within the ZIP file just like accessing a directory.
BIN Preview Handler: This will show the hexidecimal code within a given .BIN or .DAT file
XAML Preview Handler: XAML (Extensible Application Markup Language) is a Flash like format

Downloading and installing the Preview handlers is two step process:

1) Download and install Microsoft Visual J# Version 2.0 Redistributable Package (The Preview Handlers package requires that)

2) Then download the sample code from MSDN from here and extract it to a folder.

Run PreviewHandlers setup.msi from a directory called PreviewHandlers\Installer in the folder where you extracted the EXE.

Now, you should be able to preview the above mentioned file types directly from an attachment in Outlook 2007 or from Vista’s Preview Pane