@AC - Probably yes, MS have said you can downgrade to XP from 7.

You will get a virtual image with XP installed in the compatability mode, with the ability to run the applications nativly on the W7 desktop. (think Parallels or VMWare fusion for Win7)

You will need a CPU that supports virtualisation though.

And probably a bucketload of memory. :)

http://community.winsupersite.com/blogs/paul/archive/2009/04/25/windows-xp-mode-internals-part-1-overview.aspx

http://community.winsupersite.com/blogs/paul/archive/2009/04/25/xp-mode-fun-ie-6-and-ie-8-side-by-side.aspx