just for advance ( Iphone 3gs newboot untethert)
 

if you have iphone 3gs with new boot and it is tethert after update to 4.2.1 FW BB 6.15 and unlocked

here is the solution

1- as above mentioned it is FW 4,2,1 BB 6.15 tethert
2-restor with itunes to orginal FW 4.2.1 then get error 1015 ( no problem )
3- use iREB 4.0.x-4.1-RC2 to enter iphone DFU mode
4-restore again with itunes with custom firmware 4.2.1 BB 6.15
5-iphone stuck at emergency call better to activated it with sim
6-use gp_win_rc6_final to jailbreak
7-add www.repo666.ultrasn0w,com source then install

,,,,,unlock untethert ,,,,,,,

tested 100%

you can find all programs in the search buttom

please without comment just say thanks if it is usefull