Did you try to change the language in the Control Panel > Regional and Language options?
In Regional and Language Options;
1] You should see 3 tabs, "Regional Options", "Languages", and "Advanced". Click the Advanced tab. In the pull down box, can you see "Croatian" and "Croatian (Bosnia and Herzegovina)"?
If so, select the one you want.
2] In the Languages tab > Details button, can you select a different language in the "Default input language" pull down list? If so, can you then add Croatian to the "Installed services" section?
When I got my HP laptop it has Win XP on ti. and before few days I restore Win and they are now in SLOVENIAN language. Even when I tried to change language in Regional settings they are in Slovenian. I downloaded CROATIAN LANGUAGE INTERFACE and when I tried to install it i see message "ON THIS COMPUTER IS ALREADY LANGUAGE INTERFACE PLEASE UNINSTALL...". how to uninstall that? and it's not in add remove