Some suggestions for you, based on the School of Hard Knocks:
First, don't mess with that Windows 10 "disk" . It is your fall-back and fail-safe if you can take it out and store it in a static-free bag.
Go get a new SSD of 512 MB or better. The more empty space on an SSD the better for long life, so go as big as your budget allows, then install it.
Boot from your USB key, and assuming the system runs to your satisfaction, including a network connection, start the Linux installation.
Once the installation is complete, shut the system off and remove the USB key.
Your system restart ought to be fast enough to make you smile. You'll be reading all the initial system setup information and staying busy for a bit as you configure the system and add software from that huge list of available free programs. FreeDoom anybody?
Later you will almost certainly find there was something on the Windows 10 drive that you didn't back up /transfer. Because you set that drive aside, you can now use a USB adapter to connect it to the Linux box, and Hey look at that! you can browse the files on that drive and search for the pictures or whatever you are missing. Once done copying stuff, unmount the external drive and store it away again. Repeat as required
If, for reasons that seem good to you, the Linux system does work out, then you can unplug that Linux SSD and reinstall the Windows 10 drive. Should you have a HD with Windows 10 on it, I bet living with the new SSD will have you wanting to transfer WIndows 10 to that SSD, but that is a topic for another day.