Comment 7 for bug 49217

Unfortunately, the codepage cannot be determined automatically from inspection of the filesystem, although exhaustive search of the names of the files present may provide some guidance. In Windows, the codepage is set manually, and the set of valid codepages is defined at kernel compilation time. The codepage of a filename is set at the time of file creation, by the active codepage in the system, meaning that it is possible to create a FAT32 filesystem that is internally inconsistent by creating files with different DBCS encodings (which may require different installations, depending on the set of valid codepages for each installation).

While user input is not ideal, the other alternatives are to use a different default codepage for the selected language of the install (as is done for Windows), or to attempt to determine the default codepage setting for the installed version of Windows (e.g. reading CONFIG.SYS). Note that adding support for a user-selected codepage would be a significant improvement over the current state, where users must boot an alternate operating system to safely check their disks, and may need to manually partition: allowing the option to set a codepage would allow users to continue without the errors described, at the cost of some hassle.