I'm currently in the process of evaluating the design, and possible reimplementation of an in-house app our engineers use.
Although the application handles large amounts of data. Only two sets of values (floats) are saved along with a simple name and description of the data. In my opinion the current application is in overkill territory using a normalized access database to store what evaluates to 7 fields of strings and floats.
At what point do you start looking at transitioning from a flat file or serialized XML to a relational database or vice versa?