XamlViewer is an application written for the WinFX SDK (March 2005 CTP) Avalon bits. This CTP release has a bug with registering the Xaml file association. This little application fixes this, and in fact, even associates itself with Baml (binary, or compiled Xaml) files. The Baml files load faster by Avalon’s PresentationHost, because its records/nodes’ length is fixed.

Using XamlViewer
It’s highly recommended to place the executable file inside the %WinDir%\\Microsoft.NET\\Windows\\v6.0.4030\\ folder so you can make sure it won’t be deleted accidentally (otherwise the file association will brake). After that, run the executable once to create the file association.
You can use the application from both command line and even directly from Windows Explorer - just double-click any Xaml or Baml file.

Command Line Switches:
XamlViewer fileName
/b Indicates whether the selected file is a Baml file. You can skip this switch if you are sure that the selected file’s name ends with .Baml

The Package
The Zip package contains the application executable file (+ 2 pairs of sample files, compatible with the March CTP’s syntax: Xaml and Baml sources of Desktop Aurora and an “Avalon Shield” vector graphics for Mar 2005 Version).

Download: XamlViewer for Avalon Beta1 (latest)
Download: XamlViewer for Avalon Beta1 RC
Download: XamlViewer

More links can be found here.