My ps3 hardrive space is mysteriously shrinking! i hardly have anything downloaded?

i have 8 game files one demo five pictures and 2 videos and somehow my 60 gb ps3 is now down to 38 gb. quite a while ago a file popped up on my ps3 that said widows media player it looks like a white box it said kelly on it i dont know anybody named kelly. it had music and even picture files that id never seen before but inside them was blank no pictures or music. i tried deleting it but i couldnt then one day it just dissapeared. im confused.im thinking it might have taken up space on my hardrive but i dont know. now everything is normal except for the 38 gb left. i know 38gb is plenty but i want to know what happened and how i can get my gigabytes back. could it be a hacker? i dont see any huge file that i can delete. im stuck. please help!