I often find myself writing custom XML generators in ASP.NET using Http Handlers. To test my code I want to open my browser and render the XML - naturally.
In the days of IE6 all was good - I could render the XML and Internet Explorer would show me a nicely formatted view of my XML with collapsible nodes (as above). Since the inception of IE7 I've noticed this nice feature is broken (at least on the few machines I use). I chalked this problem up to the new RSS viewer, built in to IE7, and have got along by saving my XML and opening the result in Visual Studio (or some other XML editor).
Today I was done with the extra effort in the XML debugging process, so I decided to see what was up IE7's butt as to why it would not render my XML. IT seems that the RSS viewer had nothing to do with it, the problem was a result of a missing MSXML3.DLL registration (go figure), the following command issued at an elevated command line followed by a browser restart fixed all for me:
regsvr32 msxml3
Before all your Fire Fox fans start jumping up and down (yes, I use FF too).. I know FF always renders XML without issues, but I was tired of installing FF on each and every Virtual Server I found myself on developing dynamic XML.