pcx-files can be opened by a multitude of free photo editor applications.
For instance, IrfanView.
Previewers are not part of Outlook but a part of the application that adds
support for that file type. For instance, the Word Previewer is a function
of Word 2007. If you were to install Outlook 2007 but not Word 2007, then
the Word Previewer is not available either.