The Intel Classmate is a relatively inexpensive laptop convertible that was inspired by and intended to compete with the XO laptops from OLPC. I'm not sure what Classmate model this is, but I have confirmed that Argentina did buy this laptop to deploy in schools, and I've confirmed that the XO software will replace the default Windows install.
I don't know the specific reasons for replacing Windows with Sugar (that's what the XO operating system is called), but I would guess that Argentina did this because Sugar has an active and tight knit development and support community for educational software. You can't really say the same for Windows.