how to reset my sony Ericsson T517 so that resume music has not song after its name?

[Nimz]

i got a sony Ericsson t517 today but now i want to sell it but i had already put one song on there when i played it i come now on resume music but i want to remove the songs name after the resume music tab so i can sell it on i have tried deleting the song but it is still there so i just bluethooth the song back as the resume button keeps on saying failed after i delete it but still shows the name of the song