IPHONE 3G HELPPPPP!!!! PLEASE!!!!!!!!!

Hello I have an old Iphone 3g what was unlocked. It was working fine before I (without knowing) erased all data and reset settings under the settings tab. Now the Iphone won't go to the home screen. It was stuck at the apple logo and now I got it stuck on screen with the itunes logo and the white cable. When I try to restore it in itunes it just gives me the 1015 recovery error. I don't know how to get it back!! Please help!!

It was on the ios 4.2.1

Im using a mac