My dad has an old iPhone 3G. It's no longer used as a phone and my sister uses it only to run apps. I updated it to iOS 4.2.1 from iOS 4.1 and all 3rd-party applications no longer work. I synced it with my MacBook but the iPhone was synced on my dad's old work laptop but the laptop was returned to my dad's employer and he has since received a new one (unfortunately, the newer laptop is from a different employer and I don't think my dad transferred files from the old laptop) so I don't have access to the "original" computer that it was synced with. Will the delete/install application trick work with this or I have to authorise my computer with my dad's Apple ID (all apps are purchased via that account)? Or, if I use my own Apple ID and download a free app...will it work with that too?