O.K. NOMAD MUVO help needed

[Swimmer]

When I was lucky enough to receive this device from one of the members here I deleted all of his music. I then uploaded some of what I liked to accompany me while walking on the treadmill. I was only able to upload seven or eight songs, while I thought I had deleted all of the former owners music, all 256 songs, it turns out I didn't. That didn't bother me, because it gave me enough music to get me through my 3 or 4 mile walk. So now I am bored with my original choices and want to update. Well I can't, because although the device says no songs, when I open it up using the my HP computor to look at the available space it says, under READY BOOST, that I only have 40 or 50 MB's left, which means all of the songs the original owner uploaded and the ones I uploaded are still there. I try to delete the cache and it wont let me. Says I need permission. How do I get into this to delete the cache so I can roll over my choice of music. Or how do I discover, or get to, the list that is there, hidden somewhere, on the Muvo's hard drive and delete them one at a time. Thanks