It's not the best option since you will lose all your date, but you can try the HARD RESET. If you want to save something, extract the MicroSD memory card if you have.
I think Microsoft synchronize your contacts with OneDrive but I'm not sure if it always do or only if you configure the phone to save it's settings via Cloud.
So it's a bit tricky and I have never tried it as my Lumia 720 usually works with Soft Reset, but the hard reset guide says:
1) Turn the Power Off.
2) Press and Hold the Volume Down.
3) While still holding the Volume Down connect the charger or USB cable to PC
For about 8 seconds you will see an exclamation mark (!) on the screen if steps are done properly. (When you see the mark you can release the Volume Down key)
Now press the keys in the following order:
1) Volume Up
2) Volume Down
4) Volume Down
I repeat I HAVE NEVER TRIED THIS and ALL YOUR PERSONAL DATA WILL BE DELETED, but it seems legit to me and if I need a hard reset solution I will try it.
IF YOU CAN CONNECT THE PHONE TO YOUR COMPUTER AND BACKUP YOUR DATA YOU WON'T LOSE ANYTHING BUT YOUR APPLICATIONS AND CHAT HISTORY
Source Web Site where I found the solution:
PS: This looks like playing super mario, vol up, vol down, power ... it should be a bit wired to accomplish but I hope It will do the job for you :)