Orthogonal Software
Orthogonal Software was/is a company run by Scot Becker that worked extensively with the Visio ORM tools. However, his site (www.orthogonalsoftware.com) is currently not active.
Scot's Orthogonal Toolbox add-in for Visio for Enterprise Architects can be used to export XML for model files from Visio. Opening the XML file in NORMA (use Open With... and choose the ORM designer, or rename the file with a .orm extension to open directly in NORMA) will automatically convert the file. Unfortunately, no diagram information is supported, but most of the model information should import cleanly.
As Scot's site is down, we've taken the liberty of posting the last version we have of his toolbox add-in here. ORM Solutions had no part in creating this software and cannot can't promise anything about compatibility with your Visio version. However, when this works, it saves a lot of time in importing models.
Download Orthogonal Toolbox Add-in