Here's an interesting article that came through an email newsletter I get. Microsoft wants even more of your money...

You Can't Virtualize Vista Home Basic or Home Premium Editions
Microsoft is tightening its virtualization licensing in some versions of Windows Vista. The EULA for Vista Home Basic and Vista Home Premium states that, "You may not use the software installed on the licensed device within a virtual (or otherwise emulated) hardware system." However, you can use Vista Ultimate within a virtual hardware system. The biggest losers are Macintosh users. Now that Mac runs on Intel x86 hardware, many Mac users run Windows virtualized through a product such as SWsoft's Parallels. This licensing announcement makes that a more expensive option.