I thought at one point that Hyper V ran on Vista x64, but I can't find any way to install it. Everything I've found online refers to 2008 server. I'd love to run Hyper-V on my desktop for test environments.
Could you please clarify? Windows 7 is a desktop OS rather than a server system, so does not include the Hyper-V hypervisor. It does have Virtual XP mode (in the top end of the product range - I believe Ultimate/Enterprise edition), but that isn't using Hyper-V for performing the virtualisation.
Perhaps what you might have meant to say was that you can run the Hyper-V Management Tool on a Windows 7 PC, using it to manage another Windows 2008 Hyper-V box. That is definitely possible - you just need the RSAT pack.