FAT Corrupt

Is the REW button the power button at the top?  I  held down the power button while plugging into the computer.  The green screen was on for about 90 seconds; then the FAT corrupt message came on for about 10 seconds.  Then the screen on the device showed that it was connected.  But  Windows Media Player is not showing that the device is connected.  When I go to “sync” in Media Player, it says to connect device.  What is MSC mode?