tap delete repeatedly as soon as you turn it on and don't stop sometimes the opportunity to hit it goes quick or before the monitor can come on. if that doesn't work a BIOS flash may help but lets not go there yet.
Also as was said we need some more info. what is the error you get if it gives you a BSOD. or check the system event veiwer. are you doing anything specific when it crashes? a specific program, gaming, heavy CPU or gpu use? Does it crash while you are using it, or while its just sitting idle? we can't point you toward what to test without more info. could be heat, bad memory, bad part, bad windows install, virus,, memory, power supply etc. etc.