Running Mac OS X on Hyper-V
Solution 1:
As far as I know, Mac OS X (or at least leopard) will not work on a virtual machine without heavy modifications. One attempt was "released" illegally here (no links to actual copyrighted files included).
Mac OS X's architecture is different and requires EFI emulation among other stuff.
In addition, I believe it's against the EULA to run Mac OS X on anything but apple hardware (antitrust anyone?).
Solution 2:
The only virtual environment Mac OS X works on is... Mac OS X. Using Parallels you can run OS X and OS X Server on a Mac running OS X.
Apple, under no circumstances, will license OS X to run on anything but a Mac.
Obviously, given that there are Hackintoshes out there, it would be fairly trivial for VMWare et al to virtualize OS X, but Apple just won't allow it.