Yes. That's the one that I was trying to think of. I paid for a copy years ago. Still have it. But it sounds like we might have to check "hundreds" of files, unless we just focus on the commonly modified ones.
There's been some updates where it was easier to move the modifications to the new files. It sounds like a lot of the updates were stripping trailing spaces, converting spaces to tabs, etc. Unless you're very familiar with your own changes, it's going to be difficult to update to this one using any simple file compare - most lines will trigger differences.