Try to repair your computer with a Windows 7 Boot disk/USB's startup repair, pero mahirap na mag hanap ng untouched Win7 ISO ngayon for your particular system, baka kasi makasira lalo yung mga pre-activated ones.
Ano bang loader ginamit mo?
And BTW you can still save your files, provided your files are in the C:\ partition, huwag mo muna i-format kasi pwede pa yan masalba with a different computer na may SATA adapter (usually mga pc repair shop, or kung may mahiraman ka ng laptop pwede ka rin mag bili ng sata connector for your hard drive).
If kaya ng specs mo mag upgrade ka nalang sa Win10. I can provide you with help in PM if you want to install it yourself.