Make sure the PBL files that contain the DataWindows used by a Web Forms application are copied to the directory specified by the PBLibDir global property.
By default, the PBLibDir global property assigns C:\~PL_ as the directory for application PBL files. This corresponds to the File\Common\C\~PL_ subdirectory of the applicationName_root directory in the server’s virtual file system path.
On Vista and later, TreeView DataWindows are not visible if you have not given the IIS_IUSRS group full permissions (including write and delete) to application directories. See Application Directory Permissions.