Music Rollsback to what it currently is

I had my Sansa Fuze for awhile but i have not been using it for awhile because i thought it got trashed i now see that the only real problems are that the text is a little messed up and most important i cant add or delete any of the music on it!! I'v done some attempts to fix it but i jus can't get it to work,

When i format it VIa the options in your Sansa Fuze and it DOES wipe the memory BUT when i try to add new music Via my computer it simply rollsback to its old music..?

When i try to format via MY COMPUTER it simply doesnt let me it says Windows cannot complete the format or something

I have tried switching the USB mode but still no results.. If somebody could help it would be GREATLY appreciated