There is probably a way to do a factory reset, alsas I don't have one and can't tell you , but.
You might try Sansa Support themselves.
NORTH AMERICAN TECHNICAL SUPPORT
1(866) SAN.DISK (North America)1-866-726-3475
7 days a week:
4:00 am. - 10:00 pm. (PST)
7:00 am - 1:00 am (EST)