To reset Nokia E71 use any of the following procedure:

option 1 : - soft reset:  *#7780#

option 2: - hard reset:  *#7370# 

option 3 " If you have any issues with the phones software and you can't see or type anything use the hard format code:

switch off the phone. 

then press and hold green dial button * 3 while switching on the phone. 

After the phone boots let go at the buttons and begin with the phone setup.

No matter which code you use the default security code will be: 12345

since this will erase all data its recomended that you backup all the data using nokia suit before  you use these codes