Windows XP supports UNICODE, that means a single OS can display different languages (e.g. simplified Chinese, traditional Chinese, English, Korean, etc.) at the same time. However, in order to accomplish this, those software must be UNICODE based. Currently, there are still a lot of non-UNICODE software. Windows XP can still run them, but before execution, you have to change the system locale first.
The Microsoft AppLocale (or Application Locale) utility is a temporary solution to these limitations caused by non-Unicode applications running on the Unicode (UTF-16) based Windows XP. AppLocale detects the language of the legacy application and simulates a corresponding system locale for code-page to/from Unicode conversions.
Unicode based platforms, such as Windows XP and Server 2003, emulate the language environment required to run non-Unicode applications by internally converting application's non-Unicode text data to Unicode using a system wide variable commonly called the "system locale" (or "language for non-Unicode applications"). The language of the non-Unicode applications should be the same script or family as the one defined by the "system locale". Failing to meet this condition results in display of garbage characters in the UI of the application.
The AppLocale utility allows users to run a legacy application without changing to the code-page/system locale needed by that particular application. AppLocale emulates the code-page required by that legacy application without changing the machine's system locale. This emulation is only applied to the application that has been chosen during the AppLocale configuration wizard.
2 Oct 2003