The easiest way is using a linux distribution.. You can try downloading the latest ubuntu based distro known as Super OS (link - http://hacktolive.org/wiki/Super_OS) , burn it to cd and boot it into live mod.. Connect your phone and run gparted (preinstalled in the OS) . From gparted you can convert ya Sd to ext3, ext2, fat16, fat 32, ntfs, swap and so on..