This sound comes from MSN Messenger, the hugely popular instant messaging service used on Windows PCs in the 2000s. The new message alert became widely recognizable because millions of users heard it daily during online chats. Long after MSN Messenger declined, the clip stayed alive in memes, nostalgic edits and videos about early internet culture. It is still used because a single second immediately signals desktop messaging, online status lists and that distinct pre-smartphone era of chatting with friends.