You can have the hard disk removed and connected as an additional disk to another PC. When the system is on, then repair your data/save data. Then format it and restore the disk in your computer.
Or, get a windows bootable disk, windows repair disk. One can make it on another pc using the windows - to prepare system - bootable disk. If that is available, you can start your computer with it and if that works, well. you can save data and format the disk.
Or, get some disk that works on another pc. Get it Connected on your pc and repair your pc.