1- Install newest version of iTunes while do not connect your iPhone, iPod or iPad yet.
2- Once installed, run new iTunes for a while then close it.
3- Windows users simply go to folder
C:Documents and SettingsApplication DataApple ComputeriTunesiPhone Software Updates
Mac users need to locate it. I don’t really sure where it is.
4- Cut and paste files there to somewhere else.
Do not delete them in case the steps does not work for you, you can still copy them back to the folder. You can find out your username by pressing Ctrl+Alt+Del.
5- Put your iPhone into DFU Mode
6- Finally, proceed with iOS 5 restore procedure
Well, actually there is another way to fix error 3002 on Windows 64-bit using custom iOS 5 .ipsw created with Sn0wBreeze:
1- Go to C:UsersuserAppDataRoamingAppleComputeriTunesDevice
2- Cut and paste files and paste them somewhere else
3- Take the recently .IPSW file created with snowbreeze and paste it on this folder and rename it to “x12220000_5_Recovery.ipsw“.
4- Then, go back to itunes
5- Enter DFU mode >> restore >> hold [Shift] to restore >> select the file on the folder C:UsersuserAppDataRoamingAppleComputeriTunesDevice and it will work out.