Dear Yoonji,
To use Unitex, you need a private directory, or personal working directory (user manual, section 1.6). It is recommended to use this directory only for Unitex, because each of its subdirectories must correspond to a language.
I suggest you to set your private directory to a new, empty directory. To do that, use the "Info>Preferences...>Directories" menu (user manual, Figure 1.4). The list that appears in your picture was the list of subdirectories of your current private directory, so you have to set it to a better choice.
Best regards,