My laptop crashes very time it boots.

I have a computer that has been infected by some virus. It does not let me open certain programs and such. I tried to boot on safe mode but if I boot under any safe mode it crashes. So I changed the boot menu in the system configuration to boot under safe mode when it starts up to see it this would solve the problem. But now ever time I turn it on, it crashes because it starts in safe mode. So I don't now how to get back into windows to change that setting. Could someone please help me with this issue. Thank you.