To open a URL from a .NET application, many sites (including on StackOverflow) cite this example:
Process.Start(\"http://www.google.com/\");
I've tried many a solution but as i'm in a UI project (wpf or winform) I ended up using an embedded browser control. Calling navigate, setting the url then target to "_blank" launches an external browser window.
_webBrowser.Navigate(uri, "_blank");
Hope this helps. DC