Changing a file's extension in Windows results in what?

When a file's extension is changed in Windows, the file typically remains readable by the operating system, as the core content of the file is not altered by simply modifying the extension. The extension serves primarily as an indicator to the operating system about how to handle or open the file. For instance, changing a file from "document.txt" to "document.doc" does not change the actual content of the file, and as long as the file is in a supported format, the operating system can still access and read the file content.

The other options suggest consequences that do not occur merely from changing a file's extension. The file does not become unreadable or lose its original content simply due to the extension adjustment, nor does it restrict access to only administrators. Thus, the correct understanding focuses on the nature of file extensions and their role in file management within the operating system.