title: unknown extensions blocked by IIS
body: <p>I ran into a rather.. interesting problem.</p>
  
  <p>.por is not a common extension, though it is used by hero lab's for their portfolio of characters. Putting it on my win 7 laptop with IIS 7.5, the filename will be there when a directory listing is generated by the server via directory browsing and using a web browser at the local host.</p>
  
  <p>BUT, attempting to download it results in a 404. The file extension itself points to a real old corel draw file format. This behavior I can replicate easily with a .junk extension as well.</p>
  
  <p>/why/ is this happening? I would like to know not only how it's configured to behave that way but what modules are involved as well.</p>