I should note that depending on which internal drives are used - you can use them like external drives for backups. You can copy files and images there, then easily disconnect the sata cable. Then you can’t overwrite it by accident during install. But you get to use the large size of the drive for images and whatnot.
It sounds like you have enough drives to do this super safely with zero chance of screwing things up :)
Um, let’s just clarify a bit more just in case.
You have your pictures, music, videos, and other personal files on what?
On the internal hard drives (hdd/ssd/nvme/whatever) and the backup/copy of those files on the external drive (external usb hdd/ssd, flash drive, NAS, whatever)? Presumably both are formatted ntfs?
What I described above is the ideal scenario. It could be as simple as formatting your internal drives and installing Linux, then copying those files back to your newly formatted internal hard drives. This is going to be fine as long as you are SURE your backups are good. Linux can read ntfs drives and copy files from them.
I’m always a bit paranoid though and I like to take extra steps. Sometimes, you forget to backup a file. Like a save game file sitting in a random game folder, a configuration file (like a blahblah.ini) files for program settings, or your favorites, you get the point. This stuff usually isn’t a deal breaker - you really only care about the stuff that’s irreplaceable like pictures and home movies. But it’s annoying…
So what I like to do is to take a drive image. Not a backup - a bit for bit clone of the internal hard drives. Then you can’t forget anything ;) Pick your program of choice - I’ve used macrium reflect successfully in the past and it was free - it’s been a while and there may be better options these days. Make that image and store it on a large external drive/nas/whatever. Then if you screw something up - you can simply restore your windows computer or go grab that file you forgot in your backup routine. I usually keep both my “backup files” and the drive image for a good long while after I reload a pc. Sometimes it’s months before you realize you’re missing something.
So in summary/my advice.
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I’ve used it since the 90s, but windows was always my daily driver. Linux always worked, but games could be spotty and there always seemed to be to be the random breakage for no reason.
But that changed a few years ago. Games “just worked”, device support became really good, and if I’m being honest - I became a gnome guy. That interface is very very productive, especially on a laptop with a trackpad.
And then windows just, started sucking. They break machines with every single update, it’s like there’s zero qa anymore. And the little things became more and more annoying - the pop ups “upgrade to 11, try copilot, OneDrive isn’t working omfg let me help you fix that” the “where is that setting moved to now” game, the extra clicks everywhere.
My dual boot setup found a windows drive that was never being used anymore. I didn’t switch, I just stopped using. Eventually I just deleted the partition and use it for extra space and playing around with other OSs.
During this process I distro hopped quite a bit and eventually settled on fedora workstation. It’s been good to me on three PCs.