Various - safe mode - Troubleshoot Firefox issues using Safe Mode | Firefox Help

Security settings
Some security settings in OS X may contribute to the inability to boot to Safe Mode. If you have Apple's FileVault disk encryption technology enabled, or if you have a firmware password set on your system, then the computer will not boot to Safe Mode. To enter Safe Mode, you must first disable these options. FileVault can be disabled in the Security system preferences using the FileVault tab, but the firmware password must be disabled using the Firmware Password utility that is available in the Utilities menu in the OS X installer (You can get to this in OS X Lion and later by holding Command-R at startup).

F8 - By pressing the F8 key right when Windows starts, usually right after you hear your computer beep when you reboot it, you will be brought to a menu where you can choose to boot into safe mode. If it does not work on the first try, reboot and try again as you have to be quick when you press it. I have found that during boot up right after the computer shows you all the equipment , memory, etc installed on your computer, if you start lightly tapping the F8 key you will usually be able to get to the desired menu.

Various - Safe ModeVarious - Safe ModeVarious - Safe ModeVarious - Safe Mode