I don't know CentOS/Fedora but it is very likely that these "unknown" partitions contain an ext4 filesystem, the default filesystem on Linux. The first readable partition is the boot partition, containing essential system files like the kernel, firmware and drivers. It is formated with a fat filesystem which is also known by MS Windows. But this should not matter if you use a real disk imager that copies on low level all bits and bytes without knowing something about the file systems.
I'm not familiar with MS Windows but maybe you will find such an imager for this operating system. Anyway, you always can boot a Linux Live CD, maybe with Debian or Ubuntu and use the
dd command. For example if your SD Card is seen as device
/dev/sdb, then on the command line you can use:
ubuntu ~$ sudo dd if=/dev/sdb bs=4M | gzip > myimage.img.gz
This will create a compressed image from the SD Card. To restore it you use:
ubuntu ~$ sudo gzip -cd myimage.img.gz | dd of=/dev/sdb bs=4M conv=fsync
Try both commands before archive your backups.