thank you for your good tip. actually yesterday I bought a legal version, I just wished my product key applied to my pre-installed version of the window as well.

, but it's in vain, which I'd already known.
I didn't know the migration tip other than Mac OS X, it sounds a little different but quite useful. and I'm a bit relieved due to your tip even though it'll take some time. Now I have to start investing my time to resetting my system without worrying about losing my all data.
thanks again your good tip, and if anymore question, posting again.