There is only one file type that uses the .WSI extension:
Wise Package Studio Installer Package
Package created with Wise Package Studio, an installer creation utility; contains a collection of files that have been packaged into a single archive; can be installed on a Windows system using Wise Package Studio.
WSI files are similar to .MSI files, but are used specifically by Wise Package Studio.
NOTE: Wise Installation Studio and Wise Installation Express were discontinued on April 19, 2010.
Updated: June 8, 2010