Encrypt your smartphone from Settings.
It will protect you up to a great extent.
You could possibly disconnect your phone from the internet. Your friend will then have no chance of getting control over your phone unless he gets it in his hands.
Well I ve to agree with BadActor....the worst thing that could happen is that you would need to change your HDD. Try to format it by booting with the windows CD... Hope it works. Cheers
I did it in the following way
#1:-Go to settings
#2:- Go to storage
#3:- You will see a default write disk option which has been set to phone storage. Set it to External Storage.
#4:- Your phone will prompt to reboot. Agree with it and you are good to go.
Have you tried hard resetting it. I also had the same problem. After hard resetting it was alright. If it turns out to be a battery problem take it to the Samsung service center.