http://www.dslreports.com/forum/remark,18150258Please read. It is not recommended to force Safe Mode, because it changes the boot file to boot into Safe Mode ONLY.
This is not recommended if your computer is infected. That's because malwares can delete the Safe Mode registry keys or modify it such that you can't enter. Your computer will go into a loop and you have to reformat and reinstall as this step is irreversible.
Follow the instructions there to add a line to boot into Safe Mode.
If you do that and you can't start your PC, that's none of my business.
Not clear about the instructions, please ask.