01. First Step: View the Contents of Your iPhone
Restoring your iPhone to its original factory settings is a way to repair any damages you've done to the phone by downloading unauthorized software.
It's not guaranteed to fix your problems, but it is your best bet.
Here's a step-by-step tutorial that shows you how to restore your iPhone.
Note: If you recently purchased a new iPhone and are looking to set it up, you should read "How to Set Up a New iPhone."
This will guide you through the process of setting up a new iPhone.
Let's get started: The first step is to look at your iPhone and see if this is really necessary.
Restoring your phone will delete all of the data on it, including any pictures, music, videos, and contacts.
The screenshot above is the home page of my iPhone after I decided to jailbreak it. My iPhone was in need of repair.
Let's move on to step two.
02. Step Two: Connect Your iPhone to Your Computer
Once you connect your iPhone to your computer using the USB cable, iTunes should automatically launch.
If it doesn't launch on its own, you can start the application yourself.
You should see the name of your iPhone under the "DEVICES" heading on the left-hand side of the screen.
This tells you that your phone is connected. Now you're ready for step three.
03. Step Three: Backup Your Data
If you have iTunes configured to automatically sync when your iPhone is connected, it will begin transferring data from your iPhone to your computer.
This is an important step, as it will transfer any new content that you've added to your iPhone,
including songs and apps that you've purchased and pictures and videos that you've captured to your computer.
If you do not have it set to sync automatically, you should manually sync it now.
You can start the sync by pressing the "sync" button that appears in the bottom right corner of the iPhone "Summary" tab in iTunes.
04. Step Four: Get Ready to Restore Your iPhone
View your iPhone's information page in iTunes. In the middle of the main iTunes window,
you'll see two buttons. Click the "Restore" button, and move on to step five.
05. Step Five: Click Restore Again
After you click "Restore," iTunes will warn you that restoring your iPhone to its factory settings will erase all of the media and data on your iPhone.
If you've already synced your iPhone, you can click "Restore" again.
06. Step Six: Watch and Wait as iTunes Goes to Work
Once you've clicked restore, iTunes will automatically start the restoration process.
You'll see several messages on your computer screen, including the one pictured above,
where iTunes tells you it is extracting the software it needs to restore your iPhone.
You'll see additional messages, including a message that iTunes is verifying the restoration with Apple.
Do not disconnect your iPhone from your computer while these processes are running.
07. Step Seven: Watch and Wait Some More
You'll see a message that iTunes is restoring your iPhone to its factory settings.
You'll also see additional messages as the iPhone's firmware is updated.
This takes several minutes; do not disconnect your iPhone while it's running.
You'll see an Apple logo and a progress bar on the iPhone's screen while the restoration is in progress. You can move on to step eight.
08. Step Eight: iPhone (Almost) Restored
iTunes tells you when your phone has been restored, but you're not done -- yet.
You still need to restore your settings and sync your data back to the iPhone.
The iPhone will restart automatically; while you're waiting, you can move on to the next step.
09. Step Nine: iPhone Is Activated
After your iPhone restarts, you may see an icon on the phone that indicates it is connected to iTunes;
this will disappear and you'll see a message on the screen saying the iPhone is waiting for activation.
This can take a few minutes, but when it's complete, you will see a message saying the phone has been activated.
10. Step Ten: Set Up Your iPhone
Now you need to set up your iPhone in iTunes. On the screen, you'll see two options: Set up as a new iPhone and Restore from a backup.
If you want to restore all of your settings (such as your e-mail accounts, contacts, and passwords) to the phone, choose "Restore from a backup."
Select the name of your iPhone from the pull-down menu on the right of the screen.
If your iPhone has been particularly problematic, you may want to select "Set up as a new iPhone."
This will prevent iTunes from restoring any troublesome settings to the phone, and you will be able to sync your data to it, anyway.
But restoring from a backup can solve many problems, too, so you may want to try that first.
If you do choose to set your iPhone up as a new phone, keep in mind that the settings and other data you've added to the phone will be erased.
All of the contacts you stored on the phone will be deleted, as will your text messages.
You'll also have to re-enter some information, like passwords for wireless networks.
If you decide that setting your iPhone as a new phone is the best option, move on to step eleven.
If you want to restore your iPhone from a backup, you can skip ahead to step thirteen.
11. Step Eleven: Set Up a New iPhone
When you set up your phone as a new iPhone, you'll have to decide which information and files you'd like to sync to your phone.
First, you have to decide if you'd like to sync your contacts, calendars, bookmarks, notes, and email accounts with your iPhone.
Once you've made your selections, click "Done."
iTunes will begin backing up and syncing your iPhone. Move on to step twelve.
12. Step Twelve: Transfer Your Files
To transfer any apps, songs, and shows you may have purchased or downloaded to your phone,
you need to go back into iTunes once that initial sync is complete.
(Do not disconnect your iPhone when the first sync is done.)
Using the tabs in iTunes, select which Apps, Ringtones, Music, Movies, TV Shows, Books, and Photos you'd like to sync to your iPhone.
After you've made your selections, hit the "Apply" button that you'll see in the lower right-hand corner of the iTunes screen.
iTunes will sync the files and media you've selected to your iPhone.
You can now skip ahead to step fifteen.
13. Step Thirteen: Restore Your iPhone from Back Up
If you decide to restore you iPhone from a backup, click "Restore from a backup."
Once you press the button, iTunes will automatically restore the settings and files you previously backed up to your computer.
It can take several minutes; do not remove your iPhone from the computer while this is running.
You can move on to step fourteen.
14. Step Fourteen: Sync Away
When all of the settings have been restored to the iPhone, it will restart again.
You'll see it disappear from your iTunes window, and then reappear again.
If you have iTunes set to sync automatically when the iPhone is connected,
the sync will begin now. If you don't have it set to sync automatically, you'll want to start the sync manually now.
The first sync can take several minutes, as this is when all of your files, including your apps, music, and videos, will be transferred back to your phone.
15. Step Fifteen: iPhone, Restored
Your iPhone is now restored to its original factory settings, and all of your data has been synced back to the phone.
You can now disconnect your iPhone from your computer and begin using it.
I hope this resolved any problems you were having with the phone.