You can move this 3 files from IS folder to the data folder: Hannover DB.pack, Hannover Media.pack, JHannoverUI.pack.
The script in the IS folder must be:
mod "Imperial Splendour 2_2 DB.pack";
mod "Imperial Splendour 2_2 Media.pack";
mod "IS_Horses.pack";
mod "IS_sounds_musics.pack";
mod "IS_Artillery.pack";
mod "IS_britain.pack";
mod "IS_Flags.pack";
mod "IS_france.pack";
mod "IS_mod_BSM_4_1_Medium.pack";
mod "IS_mod_no_forts.pack";
mod "Hannover DB.pack";
mod "Hannover Media.pack";
mod "JHannoverUi.pack";
mod "ISBeffecto.pack";
Or you can keep that 3 files in IS folder, but rename them accordingly: IS_Hannover DB.pack, IS_Hannover Media.pack, IS_JHannoverUi.pack.
Then script in this case should looks like this:
mod "Imperial Splendour 2_2 DB.pack";
mod "Imperial Splendour 2_2 Media.pack";
mod "IS_Horses.pack";
mod "IS_sounds_musics.pack";
mod "IS_Artillery.pack";
mod "IS_britain.pack";
mod "IS_Flags.pack";
mod "IS_france.pack";
mod "IS_mod_BSM_4_1_Medium.pack";
mod "IS_mod_no_forts.pack";
mod "IS_Hannover DB.pack";
mod "IS_Hannover Media.pack";
mod "IS_JHannoverUi.pack";
mod "ISBeffecto.pack";
In this case it will be easer to uninstall the mod - you will have to only delete IS folder in the data folder and imperial_splendour folder in the data/campaigns folder. Then you will have clean vanilla game.
In any case, if you have clean original game, it is necessary to run the game first and preferably make a save in some campaign before installing any mods.