Many moons ago, I recall seeing statements that MSFT allowed Vista Ultimate
to be installed more than once on a single PC.
This is necessary for development testing.
No. Each installation of Windows Vista requires
its own unique license. It does not matter if you
are installing it on the same computer, you still
would need a new license for a second installation.
--
Carey Frisch
Microsoft MVP
Windows Desktop Experience -
Windows System & Performance
Many moons ago, I recall seeing statements that MSFT allowed Vista Ultimate
to be installed more than once on a single PC.
This is necessary for development testing.
Vista Ultimate and multiboot 
Linear Mode
