well your options are limited but this will work, delete what you want to get rid of, then FILL your harddrive why music or something up to the point where the harddrive is almost totally FULL and then delete the music
that way you are effectively overwriting every sector of the disk and you are good to go
also of course erase the cache of your computer and in addition to that, create a separate user and then delete the old users folder that will probably be in C:\users
those are the things I can think of without going full blast destructive mode with re installing stuff