https://www.mediafire.com/file/afrdo4wtdvcnzlo/Populous-The-Beginning-Language-Pack.rar/file

Extract the "language" folder to your Populous 3 directory and overwrite the files.

Go to the following location in your registery:

Computer\HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Bullfrog Productions Ltd\Populous: The Beginning

Double click the "Language" DWORD, click "Decimal" and change to one of the numbers below:

English: 9
Dutch: 19
French: 1036
German: 7
Spanish: 10
Swedish: 29
Polish: 21

This is what it should show after entering the number:

English: 0x00000009 (9)
Dutch: 0x00000013 (19)
French: 0x0000040c (1036)
German: 0x00000007 (7)
Spanish: 0x0000000a (10)
Swedish: 0x0000001d (29)
Polish: 0x00000015 (21)

*** Undiscovered Worlds will still be in english for some languages as it had limited language support ***

...after 3 years, italian language exist?

No, this was never made for the game.

The ones provided are just the ones that shipped with my boxed copy of the game.