Ensure that the operating system running the vSphere Client has the English language pack installed.
Right-click the vSphere Client icon on your desktop and click Properties.
Click the Shortcut tab and add this text into the Target field.
“C:\Program Files\VMware\Infrastructure\Virtual Infrastructure Client\Launcher\VpxClient.exe” -locale en_US
Note: The parameter -locale en_US forces the vSphere Client to use US English. You can force vSphere Client to use other languages. For example, to force the vSphere Client to use German, change the parameter to -locale de_DE. To force the vSphere Client to use Chinese, change the parameter to -locale zh_CN.
SO you have French windows and want and English vSphere Client ?
Here is what you do :
To force vSphere Client to use English: