Disabling the drag&drop features of the file explorer controls is pretty easy - you just need to set a couple of properties from your page code file (e.g. in the Page_Load() method):
|RadFileExplorer1.TreeView.EnableDragAndDrop = false;
|RadFileExplorer1.Grid.ClientSettings.AllowRowsDragDrop = false;
The first property disables drag&drop for the tree nodes, while the second disables dragging of the grid rows.
All the best,
the Telerik team