Baldur.ini *is* located in the main game directory. However, if you installed to any "\Program Files" directory, your efforts to change it will prove futile in any Windows later than XP. Windows will "protect" most of the files by replacing altered ones with backups it maintains from the original install or official update. This is a common complaint in the Infinity Engine modding community, and appears frequently in their forums.
You will see one copy of the Baldurs.ini under your installation directory. You can't directly edit it, though there are ways to change the content if you have admin right.
But it doesn't matter, because the game does NOT
read from that file.
I repeat, the game doesn't care what you do to that baldurs.ini under the installation directory. It doesn't load it at all.
Like Kezardin said, you want to look at
\AppData\Local\VirtualStore\Program Files\program name
and edit the baldurs.ini found there.