How do I convert ntfs to fat32 on my external hard drive?

My PS3 ran out of room so I bought a sata 250gb hard drive and a Western digital 500gb hard drive. For my Ps3 to recognize the external hard drive I need to format it to fat32 but I don't understand how to do it. I connectd it to my computer, right clicked on it and went to format, after that it says file system and It either says ntfs (or something like that) and exFAT, I ume it's that so I clicked that and then it says kilobytes but I just left that at 128. I clicked start but nothing happened. What am I doing wrong? I also tried to to the command prompt and put in format 32 or whatever it says it won't let me and I don't have permission or something like that. I really didn't know putting more space on a PS3 was this complicated :/