Bill Gates is seldomly prone to admitting blunders, but when it comes to the awkward three-finger login for Windows PC, he couldn’t have said it more clearly: "it was a mistake."

During a question-and-answer session at Harvard University over the weekend, Gates explained the history.

"Basically because when you turn your computer on, you’re going to see some screens and eventually type your password in, you want to have something you do with the keyboard that is signaling to a very low level of the software — actually hard-coded in the hardware — that it really is bringing in the operating system you expect," he said. "Instead of just a funny piece of software that puts up a screen that looks like your login screen and listens to your password and is able to do that."

"So we could have had a single button, but the guy who did the IBM keyboard design didn’t want to give us our single button, and so we programmed at a low level ... it was a mistake."

Although not everyone agrees it was bad thing; PCWorld notes that Control-Alt-Delete was the best mistake to happen to PCs. Why? "Because, as insecure as some perceive the Windows operating system to be, it could have been a thousand times worse if there were no keyboard interaction required to log on."

NBC Nightly News reports on the mea culpa in the video below: