Well I assumed you'd do that on another drive. If you want to use that drive to hold bigger files, I'd format it (losing all your data in the process, of course). If you want to do that (BACKUP YOUR DATA FIRST!!!), I'd advise you to use either ExFAT or NTFS that are compatible with almost every OS, although ExFAT is just an enhanced FAT32, with almost the same limitations, except for file size. I know there is a DOS command to convert a FAT 32 drive to NTFS, but I don't remember it, and it's still a dangerous process for your data even if it worked fine for me in the past.

Hope it helps.