Do the Sansa.fmt magic. First, turn off the Sansa, then out on hold connect it to the computer while holding the Record button. It should not be recognized as 16mb Format. Simply create a new folder inside the 16mb Format drive and rename it as Sansa.fmt. Disconnect the Sansa and it should do a force format.
That’s if it’s a v1 model only. With a v2, you’ll have to (possibly) force MSC mode by placing on HOLD, pressing & holding the REW |<< button while simultaneously plugging the device into the computer. Continue hold the REW button until it is recognized as 2 separate drives in Windows Explorer (it helps to already have Explorer open).
Right-click on the player’s icon and select Format… . Use FAT32 & do not use the Quick Format option.
Note: If you have to use the HOLD button (for either version), don’t forget to take it off HOLD when you’re done, or it won’t start up.