.pptx files are downloaded with wrong mime-type as .potx in IIS

Question

So, when downloading a .pptx file from a website hosted on windows IIS 7.5, it downloads it as .potx in InternetExplorer. Somehow it changes its mime-type. I checked for mime-types on that website in IIS and they are correct:

For potx :application/vnd.openxmlformats-officedocument.presentationml.template

For pptx: application/vnd.openxmlformats-officedocument.presentationml.presentation

So where could be the problem? It happens on all browsers, just on chrome and firefox it does not change its extension but it shows that it is wrong mime-type, and on IE it changes to .potx so it becomes unreadable. Any hints, where i could i start digging for problem?

Answer 1

Was finally able to solve this and the thing you need to do is install this on the server: http://www.microsoft.com/en-us/download/confirmation.aspx?id=3

Some explanation on the problem was found here: http://www.epinova.no/blog/lars-oyvind-bodahl/dates/2009/12/office-2007-files-behaves-as-compressed-folder/