I'm late to this thread. I guess buying a new computer is the more expensive but least time consuming solution.
I do hope you are able to save your files from that old one.
I have a feeling it was a computer virus which resulted into a corrupted OS. Usually, Windows computers have two partitions (C and D) and your OS (Windows) is installed on C. An OS reinstall would have fixed it (unfortunately all files you have on C drive would have been wiped out), or, like Astrid suggested, booting from another OS (considering you can download linux OS and make that into a bootable USB). But it can be very tedious if you haven't tried it before.