Thank you for your interest in the RadUpload control.
Inability to set the initial folder is a limitation of the Silverlight framework. For more information please preview this MSDN article
. Below is a cite from this article:
You cannot specify an initial folder for the OpenFileDialog. The first time the OpenFileDialog is displayed for an application, the
initial folder is based on the user's settings. Additional displays of the
OpenFileDialog for an application use
the folder of the last selected file.
We hope this information helps you.
All the best,
the Telerik team