Safe Mode within Startup

Hi,
I`m a newbie! Bear with me. I`ve caused the fault but I don`t know what I did or how to correct the consequence!
Unless I go into MSCONFIG, I cannot invoke SAFE MODE.
STARTUP should automatically go into the SAFE MODE Menu, if there was a prior failure. Mine will not.
I cannot invoke the SAFE MODE menu from STARTUP by presssing the appropriate function key.
Normally Windows 7 is very resilient, I would rarely have to go into SAFE MODE but if I leave my PC with the Internet on the screen turns off and no matter what I do it will not restart till I`ve pressed the Power Off button on the PC. I use the SAFE MODE in the event of some sort of Systems crash.
Help!!
Thank you.
Alan Beckley

Hi Lemur,
The F8 key is OK. You can see the menu without touching the PC if it has crashed previously.

Thank you.

Alan Beckley

Hi Lemur,
I`ve tried altering in bcdedit, unsuccessfully.
I can`t see the ADVANCED MODE MENU to move the arrows up and down.
Under no circumstances can I invoke the ADVANCED MODE MENU.
I must have switched it off but I can`t remember how!
Alan Beckley

As a work around you could go to 'power options' in the control panel & set it to never turn off monitor. Then if you want just turn the monitor off. It should still be running when you turn it back on.