My computer keeps turning on and off in a cycle, what should I do

[Jasonmiao]

When I press the power button, the computer turns on, but after two seconds it turns off again, I reset the bios and nothing works. I'm pretty sure that there is no problem with electricity, the only thing I do recognize is that my fan is spinning very fast, what should I do

 

[i7Baby]

Try starting in safe mode (F8) then disabling restart on failure - http://windows.microsoft.com/en-au/windows/advanced-startup-options-including-safe-mode#1TC=windows-7

 

[smorizio]

if one of the ram sticks is lose or bad or the mb cant set the ram speed on new mb it will power on then turn off and power back on over and over again in a over clock failure. if it not the ram if the power supply has failed and it not outputing all the power to every cable the pc wont post.