Domain trouble???

Alright, While I may be taking Network Administration we do not get to domains till later(next semester). However, a domain question has come up at home. Basically proggy my dad wrote is having trouble working on domain system that someone installed it on. Claims not to be able to find database, then goes to trial screen.

It worked just fine, apparently, until the guy decided he wanted to add users not from a local machine to the domain so that they could also use the program and its databases.

We are going to try and recreate the problem by setting up a domain at home. That may take a bit since we have never done that before and my book cops out on it(domains are beyond the scope of this book, bs.... I paid a good 100$ for that 1300 page book and it only states the obvious... and then when I need it.. grr...). So I will look up how to do and manage that. However, in the meanwhile, would any of you have any clues onto what causes said problem?

More info on dad's program. If for some reason it can't find the database it should just creat a new empty one. However, while it does that(or so I am lead to believe) it ends up not recognizing the program is paid for. But all others(other then the ones this fella added) still access it fine. So it doesn't appear to be the program. I am baffled at the moment. I may have scored gold if I could play with it in person but remotely I can't experiment. And I am not overly familar with domains.

Well if you can point me in the right direction I would be grateful. Could take a long time otherwise.

And whilst I wait for a response I'll do a web search on Domain setup. Dad has wanted one for a while now but we didn't know enough to willingly go play with it, particually when workgroups do what we need just fine.

And I know this isn't much info to go off of. But the guy sent us a one paragraph message(2 if you count both messages he sent) and expects us to tell him how to fix it. IAnd without the setup in front of me I really got no basis to go off of. Anywas domain setup here I come.. I guess.

Edit-

As a note if I dont' respond to this message after a post is put in it. I likely just forgot about. I more or less am leaving this open in case I CAN'T figure it out. No point in waiting til all other venues failed before trying this one.. why not try them at the same time?