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Re: how to erase background from image ?
Well, I highly recommend you to use another software for editing your sprites. MSPaint is really doubtful in therms of spriting and your archives cannot be recognised as a sprite some times. Photoshop and GIMP are very good alternatives to try; i preffer GIMP because for me its more simplier than Photoshop.
Forgive the lack of time in this answer.