|Did you check the drive already to see what file type is currently in use? According to Seagate your drive should already be formatted using FAT32.|
View the drive in Disk Management to see what the file type is. If it is NOT FAT32 then delete the partition and create a new partition using Disk Management. You should be able to format the external from there using FAT32.
I looked a Seatools for Windows and I don't know what happened to their disk prep tools. Maybe they are only in the DOS version. Try the above first.