No worries, let me pull up the cool tip screen for you.
Two things canb cause this error message, a corrupted File Allocation Table, (sometimes a bad file can do this too), or you’re genuinely “stuffed to the gills” on your device.
It’s easy to rule out the latter, if you can remember how many songs are on your device, or just plug in. If in MTP mode, you’ll get the cool bar graph showing capacity versus stored data. You can click on the sansa in either MTP or MSC and look at Properties. In this view, you get the “pie graph” display in Windows.
Here’s the page you need(I love visual guides).
For the propellerhead, or computer-savvy (my wife swears she’s going to find me a new beanie cap), you can connect in MSC mode and use Windows, chkdsk utility on the Sansa (when in MSC, it’s accessible as a flash memory drive. The command line command is chkdsk x: /f where x is substituted for the drive letter assigned to the Sansa and /f is a toggle, telling chkdsk to fix the errors found. Quite often, the Fuze is rrepresented as drives e and f, with the first drive latter being the internal memory.
You can shortcut the process by right clicking on My Computer and selecting manage. Under the Tools tab, you’ll simply select Check Volume For Errors to recover the FAT. Once you unplug, the device should be back to normal.
To select MSC manually on the Fuze, it’s under Settings > System Settings > USB Mode > MSC.
The Fuze has a handy shortcut to MSC, if you start with the device OFF, hold the center button depressed while connecting to the USB port. Keep it depressed until the display shows “connected”. Your communications session will be (temporarily) in MSC. As a footnote, if you’re reading this and have an e200 series v1 device (well, even the Fuze), press the << button instead to force MSC. The v1 device cabn switch to Manufacturing Mode this way, a mode you DON’T want unless doing I2C repairs, now that’s in the propellerhead realm.
Let us know if chkdsk or the linked Manage method solves your issue!