Yeah you can.
First you need to "shrink" or "resize" your ntfs partition to make room for your FAT32 partition. Then you should have a space called "unpartitioned space" or "free space" at the end of the drive. Then just create a new partition in the space you just made formatted to FAT32.
That should give you 2 partitions on your HDD without losing any data from your NTFS drive no matter what partition manager you use, just don't use the windows built in one as you wont be able to format the 800GB partition as FAT32.