When you say that it crashed, what specifically happened? Did you get a blue screen of death (BSOD)? Did the system just power off or reboot? Did you hear any strange noises from inside the system before the crash?
When you are in safe mode, which version are you using (e.g., Safe Mode with Networking)? Have you run the diagnostics tests outside of Windows?
Also, when you reinstalled Windows, did you perform a full format or a quick format? Any new hardware recently installed before the crashing started to happen?
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It's most likely a problem with your flux capacitor.