Anyway, what happens if my HD crashes or I buy another PC? Am I out of $25.00 just like that?
After it's installed, backup your hard drive (this should be normal procedure for anyone with a computer). If you get a another computer, there are programs that enable you to copy everything to the new one.
I downloaded the spine matching portion of the program (the only part I'm interested in), for only $10. If I lose it, I can easily buy another at that price and not worry about it.