"It says format is windows NT file system (NTFS). Can I change the format without wiping out all that is saved? That is probably the problem, I am guessing?"
I'll reckon that's the problem.
You need to reformat the drive to Mac OS extended with journaling enabled.
You can do this with Disk Utility.
BUT...
You need to save all the files that are currently on the drive TO ANOTHER DRIVE for the time being. They're gonna get wiped out if you don't.
So... copy all the files to another drive, somewhere safe.
Then... erase the problem drive.
Then... copy the files back to it.