I have no problem with whatever data is on the drive, but it doesn't even show up in windows explorer -- just on the devices list.
I'm in Windows 7. So it's a mystery. Not an urgent thing, but I'm very curious why this is happening.
Yes, but you will lose the data. Just right click on the drive in windows explorer and choose format
In general, to use the hard drive with both Windows and Mac then format it as exFAT.