start - control panel - clock, language, and region - keyboards and languages - change keyboards - general - add - korean(korea) - ok - ok (fron general) or apply - close all the window... you should be able to change back and forth to English and Korean.

when you see the language bar on the bottom, click on it to see if it has ko added. I usually have Korean as default which allows to go back to english with ease. use alt either on left or right to change back to whichever language you want to use.