Note: Why there was never a Winamp 4
Winamp, famously, skipped over version 4 and went straight from Winamp 3 to Winamp 5. The stated excuse was that it was a combination of versions 2 and 3, since version 3 had been poorly received, and that “2 + 3 = 5”.
However the real reason, as I understand it, had to do with Winamp theme files, called “skins”. If you ever needed to specify which version of Winamp a given skin was made for, you might have to say: “This is a Winamp 2 skin!” or, “This is a Winamp 3 skin!”.
You may have to say it aloud to yourself to realize why they didn’t want to have “Winamp 4 skins”.