Owners and users of the Apple iPhone generally report loving the phone, but they also report frequent lock-ups where the screen suddenly freezes or goes black altogether. Some report success solving the problem with a soft reset or the holding down of the sleep/wake and home buttons for the 10 second reset requirement. If this does not work, a hard reset is required to bring the iPhone back to life.
Update iTunes to version 7.4 or higher from the Apple website if you haven't already.
Connect the iPhone to your PC. You are automatically taken to the sync management page, and iTunes automatically begins syncing, or copying/backing-up the calendars, Internet bookmarks, contacts and e-mail accounts stored on the iPhone. Sync everything on the phone or pick and choose from the menu you're given. Sync everything on the iPhone you don't want to lose, because a hard reset restores the iPhone to its original state and all data added since it was first taken out of the box is lost.
Go to the "Summary" tab at the top of the screen and select "Restore" from the drop-down menu.
Wait as the iPhone hard resets. The iPhone comes back up in it's original factory state and a prompt appears asking if you want to restore data settings.
Select "Yes" to restore the synced data to the iPhone.