hi all,
before i upgrade it to 1.1.1 it was 1.0.2 unlocked and sim free, now i cannot downgrade to 1.0.2 it shows on the iphone itunes logo and cable (boot mode) but when i try to restore 1.0.2 (PC shift + Restore) it give me error (unknown error ... ) i tried it with 2 PC, same error. any help plsssssss

There are a couple of threads explaining how to downgrade, you need to follow them PRECISELY, especially the 10 seconds thing with releasing the button is important.

Follow the steps with 100% accuracy and it will work.

You should also post the "unknown error" code.

it should work untill the end then error, then you use apptap installer and it should come back to a working phone without the phone functions

First, download the iPhone1,1_1.0.2_1C28_Restore.ipsw from Apple. Then connect phone to dock, and hold down home button and power button for about 10 seconds until phone turns off. Now release the power button but continue holding the home button. After about 10 seconds the computer will detect the iphone in restore mode, and itunes should tell that the phone needs to be restored. Hold down SHIFT key (Windows) or ALT-key (Mac) when clicking the Restore button, and select the file you downloaded previously. Let the restore complete and ignore the error at the end. Now your phone should show a rectangle, but don't worry about it. Run AppTap to jailbreak your phone - it will fix it even though you get errors.

http://hackint0sh.org/forum/showthread.php?t=6637

yessssssssssssss, it works, its downgrade, thanx guys for your help