To Boot Into Safe Mode in Windows 8 you need to do some changes in the MSConfig utility, and then once you re-boot you’ll get the PC running in Safe Mode.
1. Press Windows key+R to get the Run dialog box. Type “msconfig” (without the quotes) and click OK
2. Select the Boot tab, check mark Safe boot and click apply.
3. When you reboot your machine it will start up in Safe Mode.
4. To boot normally repeat the process and uncheck safe boot.