We've recently become aware that a number of people are experiencing problems upgrading their iPhones to the latest iOS 4 software. Problems range from the upgrade process appearing to stall, to some users reporting partial or total data loss.
If you are one of those unlucky enough to encounter problems, we suggest you read the following suggestions and advice.
Firstly, if you suspect you have lost data, do not sync your iPhone with iTunes just yet. If you do, you run the risk that iTunes will overwrite any previous backup files you may have with fresh backups, which will no longer contain your missing data. Instead, browse to your iTunes backup folder and take a copy of any files or folders you may find there and save them into a completely separate location.
Under OS X, iTunes will store backups in
Under Windows XP, iTunes will store backups in
/Documents and Settings/USERNAME/Application Data/Apple Computer/MobileSync/Backup.
Under Windows Vista and Windows 7, iTunes will store backups in
Secondly, try restoring your iPhone. This seems to have resolved many issues, albeit not all of them. As mentioned above, make sure you've copied any iTunes backup files to a safe location before you try this.
Thirdly, if the restore didn't work or you are still missing data, download and run the iPhone Backup Extractor. The free version will allow you to locate and restore individual files from within an iPhone or iPad backup file - just point it at the backup files you copied to a safe place in the first step (you did take a copy, didn't you?!).
If you want to know more about the iPhone Backup Extractor, check out its site.