Create a USB thumb drive with a live Linux distribution (Ubuntu as an example). Connect it to your computer and boot from it. Mount the HDD in Linux and see if you can access the files on it. If you can access the files you could copy them over to a seconnd HDD or a backup drive.
Mount HDDs in Linux:
1. Open the terminal.
2. Enter "sudo lsblk" to get a list of devices and find your hard drive and the Windows partition on it. Write down the device path (e.g. HDD is sda and partition is 1 it would be sda1 for the Windows partition).
3. Enter "sudo mount /dev/sda1 /mnt" to mount the Windows partition into the mnt folder.
4. Open the file explorer of your Linux distribution and go to the mnt folder. Inside there you should see the Windows stuff like the Windows folder, Program files, Users and etc.
To unmount you can use "sudo umount /dev/sda1". Before you try to unmount something make sure you have no window open that has access to /mnt or you are copying any files or have any files open.
Get a 500 GB SSD if you could live with 320 GB HDD you will be surprised how fast your OS and apps will work with a SSD.
E.g.
https://www.amazon.nl/Western-Digital-Wd...B073SBZ8YH (afaik you're from the Netherlands?) or
https://www.amazon.nl/Kingston-SA400S37-...B01N0TQPQB