I made a slackware-14.2 live usb key with iso2usb.sh from slackware.com ( on /dev/sdc) but somehow managed to overwrite at least the start of my 1tb backup usb drive (on /dev/sdb). The backup drive was mbr formatted, but iso2usb.sh did a conversion to gpt & UEFI.
That disk had 2 partitions ext4 & ntfs. I would like to recover the ntfs, but testdisk barfs for the lack of libntfs.so.10. Where do I get that in x64 or even source? I may have as much as 90% of the ext4 partition backed up elsewhere but would like to recover as much as possible from the ext4 if I can get it reading again. I have made several packages recently which were only stored there.

I seem to have solved this one in the negative.

I got in on the 14.2 live distro, fired up gparted, and found my backup drive has been completely overwritten. That's messy. I'm not stitching up files from chunks as recovered by photorec. So I'll take the loss of recent backups, restore what I can, and back up afresh. Nothing necessary or vital has been scrubbed.