Need help with this pc it wont even turn on now

GothicRose

so My friend is currently having an issue with their pc they woke up this morning and when they tried to login to their pc and they press enter to login their pc starts to reboot or turn off and on over and over and it continues to do this till they turn the power supply off. they decided to clean their pc and reapply thermo paste also while they were at it and when they plugged everything back in it still did the same thing they checked to see if they plugged everything in the correct spots and now it wont even turn on now. any ideas why?

PowerSpec_MikeW

@GothicRose

Are you saying that it boots to the desktop and then reboots when they login? Or after they tried to login it rebooted and not it's stuck in the initial POST just restarting? Please list your full specs as well, motherboard being most important.