How to Do a Master Reset for a Locked Up iPhone
Apple's iPhone uses a touchscreen interface that includes a keyboard, which you use to type email, text messages and search commands while browsing the Internet with the web browser. Besides making voice calls and video calls, you can shoot pictures and videos, play music and read documents. The iPhone runs applications, or "apps," and there are hundreds of thousands of them available in such areas as business, news, productivity and entertainment. If your iPhone won't turn on, or if it locks up with the display frozen or an application that stops responding, you can do a master reset.
Press the "Home" button below the iPhone's screen and hold it for at least six seconds, until the frozen application you were using quits.
Press the "Sleep/Wake" button at the top of the iPhone for a few seconds, until a red slider appears on the screen and drag the slider, if pressing the "Home" button in step one did not solve your problem. Press the "Sleep/Wake" button again until the Apple logo appears on the screen.
Press and hold the "Sleep/Wake" button while also pressing the "Home" button if Step 2 didn't solve your problem. Hold the buttons for at least 10 seconds, until the Apple logo appears on the screen. This resets the iPhone.