How to format external hard drive to FAT32 in Windows?

use a program like partion commander as you can then choose what ever type of format you want.

1.Connect your hard drive. If it is an external hard drive, plug it in. If it is an internal hard drive, follow the directions that came with drive and your computer to install it.
2.Click on "Start" and select "Control Panel."
3.Double-click on "Administrative Tools" and then double-click on "Computer Management."
4.Select "Disk Management' in the left side panel under "Storage."
5.Note the drive letter associated with the hard drive to be formatted.
6.Click "Start" and in the "Start Search" box, type "cmd" (without the quotes) and press "Enter" to open a Command Prompt window.
7.In the Command Prompt window, type "format DRIVE: /FS:FAT32" (without the quotes) and press "Enter." Replace "DRIVE" with the letter of the drive as noted earlier.

You need to have either bootable windows CD or you have the option to format it through the other drive where yo have windows back up. And if you wwant to format other drives which do not hav any windows than you can got to command prompt and format the drive you want , it will ask whether you want ntfs or fat you select fat and continue.