As of early 2026, the primary supported operating systems are:
If you are searching for this term, you may be encountering a typo or a common internet hoax. Below is the current landscape of official Windows versions and how to safely download genuine ISO files. 1. The Reality of "Windows 121"
: Websites claiming to offer a "Windows 121 ISO" are often distributing malware, viruses, or potentially unwanted programs (PUPs). Downloading files from these unofficial sources can compromise your computer's security.