Is your iPhone 4 smartphone becoming unresponsive and won't power on not matter what you do? You can try to perform a hard reset.
Resetting the iPhone can be done in 2 ways, either a soft reset or a hard reset.
1. On your iPhone 4 press and hold both the Sleep/Wake button and the Home button for about ten seconds. After ten seconds you should see the Apple logo showing up.
2. Now try to run you phone again and see if it works.
Some people have jail break their iPhone and find that after a hard reset the still can't get the device back to a working order. If you have jailbreak or installing some Cydia app then try this:
1. Plug in the device to the computer and start iTunes.
2. Press and hold the Sleep/Wake + Home for 10 seconds.
3. Once you see the Apple Logo appears, release the power and continue to hold down the home button for about 5-10 seconds. Look in iTunes and see if your device have shows up.
4. iTunes will notify you that you are now in Recovery mode. Click on OK to continue with the restore process.
5. Next press and hold on the SHIFT button and click on the Restore button. Select the latest IPSW file and the prompt appears.
6. iTunes should now attempt to get your device back to the manufacturer setting.
7. iTunes will later give you an opportunity to restore you content from the PC. Every time when you do a sync, iTunes makes a backup so you can choose the latest backup from the sync.
If you have forgot your password then you will need to do this as reset will not work: iPhone 4: Fix Forgot Password
Once your iPhone is resetted, if you have a backup of your data you can also restore it back to your iPhone. But be aware that all your data store after the backup on your iPhone will be erased if you restored.
Now that you have your problem solved, you should take a look at how you can protect it with these top 10 cases, Protect iPhone 4S With Top 10 Cases.