Partition and Format System change - External HDD

My desktop was very old (windows), so i gave it away and changed to my old 2008 macbook pro for my desk.

My HDD is about 40% full but is formatted in NTFS. Is there anyway I can convert it to FAT system that would work with mac and other OSs. I dont mind partitioning one half and then converting that to FAT if that means, it wont do anything to the data on the drive. Very difficult for me to back up 500gigs at one place on my machine.

I have the WD MyBook Essentials 1TB edition.