Vista can not Format HDD to Fat 32. However there are freewares available to do this even on a Vista machine. Try any of the below links.
Fat32 Formatter 1.0
Download Fat32Formatter 1.0 - A software utility that helps you format drive larger than 32 GB to FAT32 - Softpedia
PS: A word of caution. All existing data on the disk will be lost. Remember to take a back up before formatting.
I was able to format to fat 32 my 80 GB externally powered HDD - connected via the USB on a Vista machine. Unfortunately my ONIDA DVD Player attempts read the HDD and hangs. I think a better player will handle this.
