I know this have covered before, but I've searched google for an hour know and I still can't get the phone into DFU mode. I installed iOS 4.0 before realizing that the beta version of redsn0w don't support 3GS. So I tried to downgrade to 3.1.3. Since I have SHSHs saved on sauriks server, I followed one the guides on how to get back to 3.1.3. I got to the point where got the iTunes error (1015 I think it was), and tried to use iRecovery. The iPhone is showing the recovery screen, and in order to use iRecovery, I had to get phone into DFU mode. So I hold the power and home button down for 10 seconds, the screen goes black, and I release the power button and continue holding down the home button. At this point the screen should continue to stay black, but it doens't. The phone boots up again (showing the apple logo) and goes back to the recovery screen. Is there anything I'm doing wrong?