1. log in in your pre installed windows 8 pro oem pc
2. use magical jelly bean to find your windows 8 pro key and saved it anywhere
3. insert any windows 8.1 pro dvd. google for this dvd
4. choose upgrade or save file and setting option.
5. after completing installation for activation use change key option and use your windows 8 oem key.
5. it says *this key dont work use another key*...
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