OK this turned out to be very simple but I thought I'd publish the fix any way. Basically, despite the fact that IE 9 doesn't have the check box previous versions of IE have that enables you to save your decission of what to do with a file of a particular type it doesn't mean it doesn't check the registry to see if an old choice (from a previous browser) isn't stored there. So the fix is to replicate the storage of a previous version of IE into the registry of the machine on which IE 9 is running. In my case it went as follows: If it's not there already create the following key path in the registry: HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\AttachmentExecute\{0002DF01-0000-0000-C000-000000000046} Inside the InternetExplorer.Application GUID key create a list of binary values using the COM name of the document opening application as a title. In my case (Office 2003): Excel.Sheet.8 PowerPoint.Show.8 Word.Document.8 If the values are 0000 the the application will open without asking the user.
Cheers Tom Philosophy: The art of never getting beyond the concept of life.