I still found this bug on Parallels 4.0.3810! I use Macbook Aluminum Late 2008 2.4 Core2duo. (Default spec) My MacOS 10.5.6 has iLife'08, iWork'08, Office for Mac 2008 and Adobe CS3 installed. I create a new VM with the custom option so I disable ALL Shared Application features (including SmartSelect) BEFORE I install the Guest OS. After that I install Windows XP Pro SP3 (Original MSDN CD Version) (FRESH INSTALL) then install a Parallels Tools. Once Parallels Tools is installed, I saw hundreds of _auto_file in the Folder Option > File Types For example .doc, .docx, .xls, .xlsx, .ppt, .pdf, .psd etc. (which are all file extensions that MacOS known) and also in regedit HKEY_CLASSES_ROOT The "Parallels Shared Application Folder" in Windows XP Start Menu has hundreds of Mac application shortcuts. (Disabled ALL Shared Application features in the configuration is mean-less) No matter I install Acrobat Reader 9.1 or Office 2007, these applications cannot register their file extensions anymore because of Parallels pre-registered _auto_file. I tried to delete these _auto_file from "Folder Option" and "regedit" manually one-by-one. But it not so convenient, take a lot of time and easily to make a mistake which harmful for the OS. Many user have experienced with this bug, please fix it asap.