Searching for "dual boot olpc" brings up a blizzard of articles from 2008 and 2009 suggesting that OLPC is going to be shipping a dual-boot Windows / Linux laptop Real Soon Now. However, if you say that it never actually shipped, then I'll take your word for it. I know a lot of plans changed over the course of the project.
I just think it's sad that OLPC didn't really take advantage of one of the main strengths of open source software-- the ability to build off of an existing codebase. Also, some of the comments Negroponte made about "open source fundamentalism" rubbed me the wrong way.