HoMM3 HD is a mod (add-on) for the game Heroes of Might and Magic 3.

If it's a save file, don't close the chat window (the data is stored in \_HD3_Data\Settings\log***.sod). You can set up an automatic backup when the game starts or daily; synchronization would have to be done manually, and I'm sure no one will upload this to a server. Ban cheaters immediately.