fenixproductions, have a look at the Beyond Compare
System Requirements, and more specifically the
Supported Windows Platforms. Although the page is a bit confusing at first, I believe you can interpret it as all versions having been tested to support the stuff at the top, and as later versions have come out the newer operating systems from Redmond have also become
officially supported. (And not that only Windows 7 is supported in recent versions, which would be a rather silly business decision with Vista at the least still being in active support from Microsoft.)