Memory not avalible on my mp3

Question

i have a jnc 2gig mp3 player that only has 150MB of space for storing songs. i have deleted all songs and recordings off the device, but when i view it in windows explorer and media player, it shows that 1.91gigs have been used up. there are no files in any of the folders on the device. why is it like this and how do i get rid of whatever is clogging the memory?