Apparently a ReadyNAS can use either EXT4 or BTRFS filesystems, and may use a RAID for multiple drives (like yours might).
Windows does not natively read those filesystems (currently), some 3rd party drivers are available, I've found their effectiveness to be mixed.
I found some interesting links with info on reading a non-RAID drive, and most linuxes (linuses? linuxii?) - most any Linux distribution - can read ext4 & btrfs.
This link Restoring Data from Netgear ReadyNAS Duo Hard Drive has instructions for non-RAID drives, should be worth a try. It sources this very very long forum thread as a reference. I'm sure there are RAID instructions available from a regular web search, if required. The basics are:
[to 6. on the original link] Get a Linux going that can read your hard drive
Here, some newer distributions may already be able to see & mount the hard drive's partitions.
If your file manager lists devices, it's possible that just clicking on the hard drive there may mount & open it.
Easiest way I can think if would be to try running Disks /
gnome-disk-utility and see if it can mount them with a few clicks. (Disks can also erase or overwrite partitions with a few clicks too, so BE CAREFUL!).
system-config-lvm is a gui lvm manager, probably not required though.
modprobe fuse This command is used to add modules to linux to be able to "talk" to the HDD
vgscan scans all SCSI, IDE and other disk devices on the system looking for LVM physical volumes
vgchange -ay c allows you to change the attribute of the HDD volume groups to "activate" and name the volume group as C
mkdir /mnt/lvm create a mount point for the volume group
mount -v /dev/c/c /mnt/lvm to mount the volume/group. [Original page's command was
ext2fuse /dev/c/c /mnt/lvm but it's apparently no longer in Ubuntu or Mint or Ubuntu's software repositories (there is a
fuseext2 package & fuseext2 binary...) It would've used the installed ext2fuse utility to support the mounted EXT3 file system. You will notice a slight delay in output until this is displayed:
/dev/c/c is to be mounted at /mnt/lvm fuse-ext2 intiailized for device: /dev/c/c block size is 16384
Once this is displayed, your HDD should be accesible.
[Use a file manager/browser to read your files in
/mnt/lvm]. Or Open another terminal window and enter
cd /mnt/lvm. You should notice a few folders such as Media, Home, etc. If you enter in
cd media then
ls, this will list the files/folders in the Media folder.