You have vista on one hard drive and xp on another and boot into each by changing boot disk in bios can you legally install the same software onto both hard drives as they are in the same computer?
My friend, dafodil, is quite correct. I feel, however, that there is the law and then there is the spirit of the law. If the publisher (unlike M$ and the OS) has made it possible to install more than once, and you intend on being the sole user of that software, then running off two boots on the same machine is in keeping with the spirit of the law. You may want to contact the publisher and see if they will support updates, etc under such circumstances, though.
Just my opinion.