Error: Quartus II active version is not 9.1. Please set 9.1 to be the active Quartus II

Description

You may get above error messages while trying to run the demo GUI applications with Windows 7 or Vista for the Audio Video Development Kit, Stratix® IV GX Edition.  This can occur when using any version of the Quartus® II software, including version 9.1.

You must use the Windows XP operating system in order to successfully run the GUI demo.