The Hyper-V management tools (MMC snap-in and associated UI) are now available for download:
These tools allow you to manage and interact with an installation of Hyper-V from your Vista computer in exactly the same manner that you do on a full installation of Windows Server 2008. Note that you need to have SP1 installed on Vista in order for this to work.
Also be aware that installing the Hyper-V management tools will create a shortcut for our MMC snap-in the “Administrative Tools” folder – which is not displayed under Vista by default. You need to enable this folder under the start menu properties to have it displayed.
Also note that you will need to enable WMI between your computer (per this article: http://msdn2.microsoft.com/en-us/library/aa389290(VS.85).aspx).