Cheats for Heroes of Might and Magic V.

In this directory, find the file "autoexec_a1.cfg":
C:/Games/Heroes of Might and Magic V/profiles/
Open it with a text editor.
Add the following line:

setvar dev_console_password = schwinge-des-todes

to the very end of the file, and save the changes.

I can't save the file. It says that the change is not possible. What should I do?