There is no way to know, really, without contacting the developer or jumping into a LOT of questions.
Can you not ask the developer?
Do you have the 'source' programming/screen/print files (.rsl, .fsl, .ssl, .lsl) or only the 'delivered' versions of those files (.rdl, .fdl, .sdl, .ldl)?
Does it use an SQL system, or local Paradox tables?
This would be a start if you can answer these. But whether you have someone who can do all the work necessary to move the program to a new system is probably the most critical thing to answer.
As far as the 'runtime files changed', whether that is true or not depends on what you have and what the person who said that intended to say. Again, no way to know without some of the above questions - and likely several others.
At least you aren't asking about moving to Vista.
Tony McGuire
"It's not about having enough time; we have the rest of our lives. It's about priorities.