Critical Stop is a long-running Windows system alert, used by Microsoft Windows to warn users when an operation cannot continue, and the Vista-era version is closely linked to Windows Longhorn, the development codename for Vista. As soundboards and video editors collected classic operating system sounds, this short chime spread beyond the desktop into memes, gaming clips and reaction videos. It remains popular because almost anyone who has used a PC recognises it instantly, so a single chime can signal failure without any explanation.