Intel is quite sure that its upcoming Pine trail-M platform will support at least two versions of Windows 7. Intel has informed its valuable partners that Pinetrail-M, mobile platform that includes N450 CPU and NM10 chipset will support Windows 7 Starter and Home basic.
Since a lot of people already tested Diamondville, Atom based notebook and windows 7 RC1, we already know that all Windows 7 versions should be able to run on existing and future Atom platforms, but Microsoft will definitely want to draw a line, and limit some Windows 7 to more expensive notebooks.
Calpella and Montevina platforms will be able to run the full Monty, including Enterprise, Professional, Ultimate, Home premium and Home basic.
It looks that Windows 7 Starter is exclusive to Netbooks and you won't be able to get it with any big notebooks.