Case of the IE8 Download Opening with Wrong Application

When moving from IE6 to IE8 a customer had this issue with a web page. A file with .SIM extension when opened from Desktop opened in correct application. However when launched directly from IE it incorrectly attempted to open in QuickTime. This problem only occurred with IE8, not IE6.

Mouse over the hyper link the file showed in status bar with correct extension – .SIM


However when right clicking link and selecting Save Target As the extension magically changed into .MOV. This also happened in IE6. The difference IE6 when using Open it opened as .SIM.


So I started a ProcMon log ( As Windows use Registry keys for file associations I set a filter to include the following Operation is RegQueryValue, Process Name is Iexplore.exe and Process Name is wmplayer.exe. I looked for the start of wmplayer.exe process and worked backwards. So I see Internet Explorer is treating the file as MIME type video/quicktime


Right clicking the selected entry and clicking Jump To we can see the reg key. We can see the registered extension here is .mov


Looking at HKCR\.sim we saw the file registration our app should be using to launch:


We also can see here the MIME type that should have been used application/x-sim

But why is it using QuickTime? As we didn’t have the luxury of IE9 Developer Toolbar in this case as in

I went to using Fiddler ( Which is an absolutely great utility for capture and analysis of http/https traffic.

The trace showed the following:


So why is this file showing up as Content-Type: video/quicktime ?

To do that required connecting to IIS. In this case it was a legacy version IIS 6.0.

So connecting to the Web Server I right clicked Internet Information Services and selected Properties. Then clicked MIME Types…


Looking at the registered MIME Types the .sim extension was set to video/quicktime


Clicking Edit fixed it up to correct MIME type


Note: MIME Types can also be set per Web Site. This will be in the individual Web Site’s properties under the HTTP Headers tab.

This changed fix the issue, .SIM file now opens correctly both from Web and Desktop.

About chentiangemalc

specializes in end-user computing technologies. disclaimer 1) use at your own risk. test any solution in your environment. if you do not understand the impact/consequences of what you're doing please stop, and ask advice from somebody who does. 2) views are my own at the time of posting and do not necessarily represent my current view or the view of my employer and family members/relatives. 3) over the years Microsoft/Citrix/VMWare have given me a few free shirts, pens, paper notebooks/etc. despite these gifts i will try to remain unbiased.
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