Interesting article by Tom Yager on LinuxInsider about Services for Unix:

Unix for Windows
In heterogeneous shops and homes, SFU and Virtual PC 2004 should be installed on every machine. These two products represent the most important technology to come out of Microsoft in almost a year. They show an easing of Microsoft's internal barriers to achieving genuine Unix interoperability.

Tom also mentions Virtual PC as a tool for running Unix and he promises a SFU review soon. I'll post a note when I see it.