Interesting, Kaycee. We regulars on here just found out a couple of weeks ago that there was this option in the new 800 series Satellites. So, I'm flying blind here but have a few suggestions.
1. When you make your selection in HWSetup, do you close the window by hitting Apply and OK? Don't be offended by my asking. What even brings that question to mind is that I and others have made the mistake of closing such windows without hitting Apply.
2. If that's not the problem, try a System Reset. Turn off computer. Remove all attachments and battery. Press and hold the Power button for 15 seconds. Attach Power and insert battery. Start computer and tap F2 at the Toshiba splash screen to get in BIOS. Press F9 to setup system defaults. Answer Yes. Press F10 to Save Configuration Changes and Exit. Answer Yes to complete the process. The computer will restart.
3. If that doesn't do the job, try going back into BIOS Setup and looking for the BIOS setting that controls that function. I can't be more specific for you since I don't have your model machine to look at. The setting is probably under a Heading like Advanced and maybe even a sub-heading like System Configuration. You will have to look around on your own. Hint, navigating in BIOS Setup is by the keyboard arrow keys, F keys and Enter. If you find and make the change there, be sure and Exit Saving Changes. The mouse is not used.
4. If still no luck, you will have to give me your complete Model info as in my examples below so I can get a certain driver for reinstallation. Hopefully, we won't have to go that far.
Good Luck!
C.B.
P.S. Be sure and let us know the outcome and what worked for you, if anything.
Thanks C.B.
Don't worry, I wasn't offended by Point 1 
I did select Apply and Ok, but nothing happened, which drove me to search out this forum. I followed Points 2 & 3 exactly as you described, but still nothing. The BIOS default setting was also Special Function Mode, as expected, but obviously doesn't actually work.
My model info is below. If you can come up with some other suggestions, I'll test them out, but don't worry about it too much...life will go on.
Toshiba Satellite C870D-00G Windows 7 HP SP1 64-Bit
Phil, all the details for your machine are located HERE. The TVAP for your machine is HERE. The HW Setup Utility is HERE. And the User's Guide is HERE and the Function keys are covered starting on page 83.
Otherwise, my prior posts apply to your problem. If you have occasion to post here again on a different subject, please start your own thread rather than piggy back on another which gets confusing to us old farts on here trying to help. 
Good Luck!
C.B.
