If you are re-setting your Lumia, and your phone seems to get stuck at the spinning gears for a long time, try the following:-
Volume Down + Power Button for 10 seconds. Then, when you see the Nokia screen,
press the following buttons, in sequence, one at a time:
The gears will spin for about 5 minutes and then will reboot to the welcome screen and stuff.
You may have to try this sevral times - just have patience. I seem to remember I had to try about 10 times, before my phone finally sprung to life.
Kudos to Alexandre Chohfi - Nokia Developer Champion
There is now an alternate method if all else fails - How
to easily fix the Lumia reset spinning cogs at home courtesy of My Nokia
Originally posted 13/Sep/2013