Here's an easy one -READ ALL THIS BEFORE YOU START.
Make sure you do all this connected to tour computer. I'm going to show you how to your device into DFU mode.
Firstly hold both the home and sleep buttons of your iPhone/iPod Touch or whatever together for 10 seconds.
You should hear the device disconnection sound from your computer.
Once you hear the sound, leave the sleep button and keep holding on to the home button.
You will hear the device connection sound. If your speakers are busted, then hold on to the
home button for about 25 seconds.
If you have successfully got your devices into DFU mode, then you will have a blank iPhone screen an won't be able to turn in the phone by pressing the power button. If that happens you are not DFU mode.
If you get to a screen with a cable and the iTunes logo, then you are in recovery mode.
Try resetting your iPhone by holding down the sleep and home buttons together until the iPhone goes off. If your phone keeps going to recovery mode , then read my next post.
To get out of DFU mode, just keep holding onto the home and sleep buttons until the apple logo is seen.