In order to manage Hyper V host from client computer, you can download
RSAT for Windows 7
Download:-
http://www.microsoft.com/downloads/details.aspx?FamilyID=7D2F6AD7-656B-4313-A005-4E344E43997D&displaylang=en
Supported Client operating system:-
Enterprise, Professional, or Ultimate editions of Windows 7
Both x86 and x64 are included with Hyper V snap-in.
RSAT for Windows Vista (With Hyper V snap in) - only x64
Download:-
http://www.microsoft.com/downloads/details.aspx?FamilyId=D647A60B-63FD-4AC5-9243-BD3C497D2BC5&displaylang=en
Update:-
http://www.microsoft.com/downloads/details.aspx?familyid=D826C426-9690-4CA8-82BA-25F60F1057F6&displaylang=en
Supported Client operating system:-
Windows Vista Business 64-bit edition; Windows Vista Enterprise 64-bit edition; Windows Vista Ultimate 64-bit edition Service Pack 1 (SP1) or later versions of Windows Vista Service Packs is required
I can't locate Hyper V Snap-in for x86 Windows Vista operating system.
For my testing environment, i have tested that you can use RSAT on Vista client computer to manage Hyper V R2. No problem encounter even server and client is running different Hyper V MMC version.
p/s: Using vista RSAT to manage R2 is not supported by Microsoft.
