I have an HDD with two partitions. I can format one of them as NTFS, exFAT or FAT32. The other partition - a 51.26GB partition - can only be formatted as NTFS or exFAT. Why?
According to Disk Manager they're both currently RAW partitions.
FAT32 has a maximum volume size of 32GB and you cannot format a FAT32 partition bigger than this on Windows, although it technically supports bigger sizes.
Nowadays this partition format is basically used for Pen Drives only, just for wider compatibility with any system you plug it in. It is not recommended for other uses, because it has no support to file security at all, maximum file size is 4GB etc. I don't know why you want FAT32 but if you are not sure about this I recommend you go for NTFS.