decode old file

I have a problem I need solved, not really an independent project. I have some old files that are used by a legacy application whose character encoding I can't determine. I would like to pay the first person who successfully tells me the way to decode them. I know some of the contents at the beginning of the files and have figured out that the first letter corresponds to at least the first byte. So for instance each line that when decoded begins with an "A" starts with byte(98). This extends to words as well, so each line that begins with "hello" will have the same beginning byte sequence. But I can't figure out how to split the "hello" into individual characters, ie I can't deduce the characters after the first one. Maybe the program is using a weird endianness or something. The fact that the first letters and words map directly to predictable byte sequences makes me think that the files are either not encrypted or else very weakly so. Someone with experience with old file formats or cryptograhy might be able to sort this out. If interested contact me and I'll send the files along with the text that I know appears with them.