If you are asking about getting into Safe Mode, I just posted the process to enable the menu in another thread:
http://www.tomshardware.com/answers/id-1917582/windows-allowing-safe-mode-freeze-system-recovery.html
The Shift + F8 method doesn't work, and F12 has never worked (it was never the command to access the menu on a system with Windows installed. F12 was generally a key used to access the BIOS/UEFI boot menu, which is different). What is really happening when someone claims that the Shift + F8 method works is that they are hitting the F8 key (Shift actually has nothing to do with this) within the narrowed time window to bring up the new Advanced boot options menu.
Microsoft changed the boot loader to restrict the time window to press the F8 key to a whole 200ms (two tenths of a second). The thinking was that the new boot loader would detect and fix boot up issues either by itself automatically, or be called upon by the system within that 200ms window after several failed bootup attempts, while giving the user a bit more control of the system after attempting automatic repairs... the user would not need to manually call upon the advanced startup options.
The problem is that this doesn't always work, and the new process for getting to the Advanced Bootup options menu when you actually still can boot Windows normally requires extra steps in Windows 8 and 8.1, which leaves most people feeling frustrated. I love Windows 8 and 8.1, but this point did tick me off a bit when I first moved over from Windows 7. I totally share your frustration here, and I hope Microsoft reverts that in future versions of Windows. When the system fails, the user needs a way to manually access recovery options. It should not be left up to the failed system to determine this.
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