In this post, Justin Angel explains what COM+ Automation is and demonstrates how to use it to perform some previously unavailable tasks in
Silverlight.
Source: Justin Angel's Blog
Silverlight 4 Beta 1 offers the ability to initialize and use COM+ classes from Silverlight.
It should be noted that these features are only available in elevated privileges Out-Of-Browser mode and are not available in-browser.
In Silverlight 4 Beta1 Com+ Automation only works on Windows machines (but more on that later).