Windows XP was released by Microsoft in 2001, and its shutdown sound was one of the short system sounds built into the operating system, heard by millions of users as they switched off their PCs each day. As XP gave way to newer versions of Windows, the sound moved from everyday background noise to a cultural shorthand for early 2000s computing. It now circulates widely in nostalgia videos, memes and edits, where a few seconds of it instantly signals an era of beige towers, dial-up internet and shared family computers.