A setup-free software application and related operating techniques are described herein. The setup-free application is contained within a package file that does not appear as a program file to the computing system. When the package file is opened, the computing system virtualizes the “installation” of the setup-free application without copying application files to the actual file system and without making any modifications to the actual registry. When the setup-free application is running, operating requests (such as file read requests, registry read requests, and file write requests) are directed to the contents of the package file. Such redirection away from the actual file system and away from the actual registry enables the computing system to run the setup-free application from the package file.