you will need to disambiguate your references to DAO and ADO always use

Dim Db As DAO.Database
Dim Rc As DAO.Recordset
Dim Arc As ADODB.Recordset..

Also if using any of the other office apps like Excel or Word, switch it to Late binding instead of early binding..

If your database was built in A2K then be aware that some functionality was not available in A97, but it should not matter the other way round as A2K is backwards compatible.

The differences between machines will depend on the versions of DAO and ADO that the machine has installed, if possible ensure that the same version of these are available on all machines.