Control Open and Save Dialog Prompt on Windows 7 and Server 2008

When downloading certain content from within Internet Explorer you may well be prompted with a dialog box asking "Do you want to open or save this file ?"

and their will be a tickbox asking if you want this prompt to appear each time.




I have had trouble finding any decent description of the behaviour for this in Windows 7/Server 2008 but do know this much.

The following registry key gets populated your choices.

HKCU\Software\Microsoft\Windows\Shell\AttachmentExecute\{0002DF01-0000-0000-C000-000000000046}

eg.  Adobe Reader Adds AcroPDF.PDF.1      (reg_Binary)
       MS word Adds         Word.Document.8  (reg_sz)


Adding these keys appears to automatically open the file and not prompt.

I think that the Editflags keys inside HKCR\.fileext may also have a part to play in this process but to resolve my issue of users getting prompted when clicking PDF files the above key was enough.