What version of windows are you using and do you have a disk for it? Some things to try before going overboard on running repair programs . First unplug the computer so it has no power then hold the power button down for a 60 second count . This will allow for a clean boot . Next if this brings no joy boot into safe mode(would tell you how if I knew which version of windows you are using) with command prompts then run an [https://support.microsoft.com/en-ca/help/929833/use-the-system-file-checker-tool-to-repair-missing-or-corrupted-system|sfc scan] this will repair most files and if not it will prompt you to run the repair disk . If it will boot in safe mode run a virus scan as many viruses emulate a system failure . Something else you may want to try is removing one stick of ram and running only one if no joy try the other one . Bad ram caan cause a blue screen error. Hope this helps