If you are running Vista, Windows 7 or Windows 2008 64-bit with Microsoft office Outlook 2007 and click on an Adobe Acrobat PDF attachment in the preview screen you will get the message
This file can be previewed because of an error with the following previewer:
PDF Preview Handler for Vista message
Open RegEdit and go to:
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Classes\CLSID\{DC6EFB56-9CFA-464D-8880-44885D7DC193}
There should be an existing AppID value, incorrectly set to {6d2b5079-2f0b-48dd-ab7f-97cec514d30b}
Change the AppID value to {534A1E02-D58F-44f0-B58B-36CBED287C7C}