Instructions to change the language of the entire system in Windows 10
1. Use the Windows + I shortcut to open the Settings app.
2. Click Time & language.
3. Click Region & language.
4. In Languages, click Add a language.
5. Click on the Vietnamese language and choose specific variations if available.
6. Select the new language and click Options (and download any language pack if needed).
7. On Region & language, select the new language and click Set as default.
8. If possible, by Country or region, choose your location to allow Windows 10 to provide you with local content.
9. Use the Windows + X keyboard shortcut to open the Power User menu and select Control Panel.
10. Click Add a language.
11. Click the Advanced settings link in the left pane.
12. Click “ Apply language settings to the Welcome screen, system accounts, and new user accounts .”
13. On the Administrative tab, under “ Welcome screen and new user accounts “, click the Copy settings button.
14. Check the Welcome screen and system accounts screen, and the New user accounts option.
15. Click OK.
16. Click OK again.
17. Reboot your computer, and when it reboots, you will see the new default language globally through the operating system.