(I don't know why I didn't think of this before, I'm so stupid!)
Hmm... I think you can actually register your NEW serial at schthacks site.
Anyone with a new serial, that was never tried online go to:
http://pages.globetrotter.net/ctrep/singup.html
There you can put in your serial/key.
This isn't an edit, but continuation from what I just typed:
Ok, I have since looked at that site and the Register page, but too many users have been registering the same key. So... if you contact schthack some how, he might be able to add that serial/key to the server list and thus let you play with a serial that was never registered*
*I have no idea if that's how it works, but I assume so because that's the impression it gives me. Basically it seems like you're getting a hunters license without going to sega