The system locale is required to run most hacks, it allows you to read foreign text that is not supported by unicode and runs some code that is not supported by unicode.
For Windows 7:
Open Region and Language by clicking the Start button , clicking Control Panel, clicking Clock, Language, and Region, and then clicking Region and Language.
Click the Administrative tab, and then, under Language for non-Unicode programs, click Change system locale. If you're prompted for an administrator password or confirmation, type the password or provide confirmation.
Select the language, and then click OK.
To restart your computer, click Restart now.
For Windows XP:
To open the control panel, click the Start button, then Control Panel.
Click Regional and Language Options.
In the Regional and Language Options control panel, click the Advanced tab.
If you don't see an Administrative tab, you might not be able to change the system locale. Contact a system administrator, or log in as a user with administrative privileges.
In the Language for non-Unicode programs section, choose the language from the list that best matches the words and clues you want to use. Then click OK.
You may be asked to install additional files to use the language you select. You may need your original Windows CD for certain languages.
Once the change is complete, you'll be asked to restart your computer. Make sure that you can find this page again after restarting, and then do so.