toshiba c55-a-1nn

i have toshiba c55-a-1nn the original windows is 8.1 i buy it in 2013 i install windows 7 (not original and hacked) i want to back to my original windows but there is no restory it should be there but when i installed hacked windows all things destroy plz plz plz plz plz plz plz can you help me...