Hi all,
So, tried to install Centos 7 onto "free" partition previously used by Ubuntu; somehow got my wires crossed and installed Centos 7 (with LVM) on the entire Windows 10 1 TeraByte drive; I'd love to get my files back, but not really sure the best way to proceed.
Any hints or suggestions?
Many thanks

Hope you've got a backup.

Any files that have been overwritten, which means the first ~5 GB on the disk, are gone. You can attempt to use testdisk/photorec to scan the drive to see what's recoverable, but it's going to find a LOT of trash that you'll have to sort through manually. Afterwards, you'll have to format the disk and reinstall Windows from scratch, and then re-load whatever files you managed to recover back onto it.

It's going to be a LONG and painstaking process. If you have a backup then use it, otherwise good luck.

It's not just the first 5 GB that's gone. Linux filesystems deliberately spread data around in all the block groups so that files and directories can be stored close to their inodes and have nearby free space into which to expand. Even in an empty filesystem, there will be blocks of filesystem metadata (group descriptors, inodes, ...) at the head of each block group. It's like shooting that NTFS filesystem with a shotgun.

You can see if testdisk's Filesystem Tools can find an intact Master File Table in that NTFS filesystem. If it cannot, all the file names are lost, and all you can get is whatever "anonymous blocks of data that might be files" photorec can recover.