Hi Lisa. You could also restore as new, not from a backup. Reference p.141 in the manual.
Basically you do the restore in iTunes which reinstalls all the software on the iPhone and wipes everything off of it. You'll want to sync your iPhone and also do a manual backup (right click on the iPhone icon on the left of iTunes and select backup). Do the reinstall of the firmware from the main iPhone screen in iTunes, then restore your backup file and re-sync all your music, videos, apps, etc.