One Program, 3-4 computers

I am writing a program for an environment and need some advice.
The program will be run on 3-4 computers, but each one needs to access the same data.
The issue is that the users are not skilled, so the program needs to set up everything.
I was using ADODB and jet as a database provider to set up a database in a windows shared folder and having the other computers access that file. I am running into a few errors with access rights though, and cant seem to serialize a class and store it in the database.
As a work-around, I was using a binary file to store the classes I needed serialized and storing everything else in the database. This isn't at all practical.
The program is nearly done, but i need to address these issues. It is well-organized code, so I am prepared to quickly swap data providers.
The other issue is that when I publish an update, if there are structural database changes, I have had to delete the database. Obviously this wont work once the user has the program. I can't tell them they are losing all their data because i forgot to make a field for a phone number...
There must be a more efficient way to do this, But these are computers are not always connected to the internet, only a LAN. So I need to manage the database through the initial install and updates.