Oracle Enterprise manager express is another language I have recently installed oracle 12c for my lab, everything went fine, but when i log on the OEM express everything is in spanish, how can i change the language back to english? 

I have the OS  (windows 2008 R2) in English and everything is installed in English. 

Thanks in advance for the help.
OEM is a web-based application so the language is determined by the default on web browser like Internet Explorer, make sure to change it to English (note you may see Internet Explorer menu in English but the default language (localization is not)) it can be change from internet option. give it a try