Issue
If you have installed Designer 7.1 and you receive an error message on starting the client that it cannot find Designer.xdc, then it looks like you have a corrupt installation. This can occur if you attempt to install a newer patch version of Designer 7.1 on top of an existing installation.
Solution
You must always completely uninstall an existing Designer 7.1 installation, before you attempt to install a newer version. You should use the Add/Remove Programs option in the Windows control panel to uninstall the older version.
reference: (181304492)