The files contain 3 new Silverlight 4 application template themes:
-Accent Color
-Windows 7
-Cosmopolitan

FOR VISUAL STUDIO 2010
==============================
To install the themes into Visual Studio 2010, double-click on the *.vsix files 
in the VS2010 folder for the basic navigation template.

For RIA Services there is a minor issue with the VSIX format and RIA Services 
templates.  In the meantime copy the RIA Services template ZIP files (as is, don't 
extract) into your %My Documents%\Visual Studio 2010\Templates\ProjectTemplates\Silverlight
folder for WCF RIA Services Business Application Templates.

FOR EXPRESSION BLEND
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To install the themes for use in Blend 4, copy the folders in the Blend4 folder 
to  %ProgramFiles%\Microsoft Expression\Blend 4\ProjectTemplates\en\CSharp\Silverlight

RAW STYLES/ASSETS
==============================
The raw assets (resource dictionaries) are available in the 
SL4Themes-RawAssets.zip file for using in existing projects or to extract 
theme elements for use elsewhere in your applications.

Sample preview of themes
==============================
Windows 7 Theme: http://www.silverlight.net/content/samples/sl4/themes/windows7.html
Cosmopolitan Theme: http://www.silverlight.net/content/samples/sl4/themes/cosmopolitan.html
Accent Color Theme: http://www.silverlight.net/content/samples/sl4/themes/accent.html