If there were a decent registry hack I would not comment at all here. But there is not, as wolluf states above. So the Holy Grail eludes as all, once again.
Honestly, while there are tons of hacks to mack at times the Windows Title appear as if it is a Server version, and a ton of mysterious registry hacks to increase limits, the APIs required are simply not there under Win2k Pro to make this possible.
Way, way, back in the pre-release days, there was little difference between Win2k Pro and Win2k Standard Server. But for any commercial release, and certainly any current release, there is no magic registry fix to the 10 user limit possible.
If there were, I honestly would not have said anything in this thread. But I can honestly tell you that there is no hack.