I think if your GPU was broken that you would not be able to start up windows or get by the Bios for that matter.
Have you re-installed your GPU drivers? That would be where I started.
Check windows eventlog and look for errors and warnings regarding your ystem.
You can also run a dism scan to check if your system (files) are Oke.
Have you heard that the "DISM.exe /Online /Cleanup-Image /Restorehealth" command can fix serious Windows errors? Learn about this command...
www.itechguides.com
If you are unlucky you might also be suffering from a failing power supply. Perhaps there is someone who can assist you in troubleshooting if you lack the knowledge.