Hi, @Quoc Minh Hoang
Thank you for posting in Microsoft Q&A forum.
The bg-BG folder in the SysWOW64 directory is a language-specific folder for Bulgarian language resources. It is not essential for the system to function properly and can be safely deleted if it is empty.
It is possible that the folder was created during a software installation that required Bulgarian language resources. If you do not use Bulgarian language features, you can safely ignore this folder.
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