I doubt it is worth anything much...I upgraded to v6 just before the buyout, and was involved in a bad car accident before I could install, and didn't get to it for almost a year. In the meantime, the whole emagic sale happened, v7 came out, etc...I was at a loss for how and with whom to register, etc. When I finally got ahold of someone in Germany who referred me to someone in Cupertino, they told me to not even bother sending in my emagic dongle. So I still have mine, too.
I figure I could install 6 on a powerbook for gigs, but other than that it's a paperweight.