First, there is no GUARANTEED way to make this work.
FAT32 to NTFS is pretty straightforward (tool in windows), the other way around needs an external tool like this: http://www.disk-partition.com/free-partition-manager.html
That said, you need to make a back-up first ALWAYS! And if you are making a backup anyway, you might as well just re-format the drive, making sure it’s a clean format, then copy back the backed-up files.
Apart from this process, I’d feel really, really uneasy if all my music sat in one, single place. So, if you can, get a second drive (minimum as large as the space currently used, doubt you have 1TB of music – and if you do you need to rethink that strategy 😀 ), make a clone (exact copy), reformat the old drive to FAT32. Then copy back the files from the new drive to the old one. CHECK if everything is there and working as expected. Finally make another clone so the new drive is also FAT32. Now you have a live copy of your music that you can immediately swap out in case of hard disk failure of your primary drive.
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