It is, of course, pointless to fix the problem if your drive is bad or PC infected so don't skip ahead. It's entirely possible that the cause of your problem will be listed. Make a full system backup if your drive is OK and cleanĬheck event viewer for errors.
Run full system virus and malware/spyware scans to ensure that your PC isn't infected. Run a hard drive diagnostic, verify that your problem doesn't arise from an imminent drive failure. Since you've determined that your problem doesn't have a simple solution then you need to troubleshoot: