It really depends on the exact terms of your agreement with the client.
If there was a written agreement, what does it say about what is and is not deleiverable to the client? If there was no written agreement, was this discussed and what was agreed to?
If there was no discussion, what "the files" consist of would depend on the normal practice and custom of the trades. Although I do not know the precise details of the software, you obviously could never be expected to turn over the Flash file from Marcromedia if its license to you did not permit you to do so.
Normally one's work notes -- reflecting the entire creative process -- would not be turned over.
The usual response companies make is to turn over what they are comfortable turning over, and nothing more. If the other party wants more, then the ball is in its court. ALso, if you haven't been fully paid for something, don't turn it over.