Hard reset: A three way key feature widely known as a function on many Symbian devices. The main purpose of the said command is to restore the phone to its factory state condition. Symbian editions that can do this are the following:
Series 60 (2001)
Series 60 Second Edition FP1, FP2, FP3 (2003)
S60 3rd Edition FP1, FP2 (2005)
S60 5th Edition / Symbian^1 (2008)
However, doing this with a Symbian^3 phone will have some adverse effect especially on the N8.
Nokia N8 3-way key:
STEP 1) Turn off the Nokia N8
STEP 2) Press and hold these simultaneously VOLUME DOWN, CAMERA KEY, and MENU BUTTON
STEP 3) Finally, press the power button, while holding the key and waiting for the phone to boot up.
Device reset would definitely work but will wipe some applications such as OVI Maps, OVI Store, and Nokia Social. Reinstalling the firmware via Nokia Suite or Nokia Software Updater will not restore the components mentioned, one way of fixing this one is by sending it to the Nokia Centre for a reflash.
If you are adventurous enough, you may download and install them individually. Solution here.