A kid down the road asked me to update his iPod Touch from IOS v3.1.3 to v4.2.1.
I was doing this on my Windows 7 with itunes. This was a fresh install of itunes. I connected the device and the first thing i did was right click & back up. It took a while because he had filled all 7Gb of the device. Sure enough, I could tell that the music was now listed in my itunes library.
Then i started the update (which decided to do its own back up again, which seemed identical to the previous because of how long it took). The new IOS downloaded and installed and lastly it said it was restoring the apps and music. That restore process was quite quick and to my horror, ended up with almost 7Gb free. So the music and apps were gone! I look in the itunes library and the music is all gone too.
These apps and music were not purchased content (AFAIK). In particular i think the apps were free ones (little games), but all these apps will need to be re-downloaded. Plus save game files may be gone.
I do not know if the device was jail broken or anything. I am not an Apple Pro.
What went wrong?
Additional
I also tried to do a restore and there was a drop down list. In that list was:
<Name's> backup 20/Nov/2011 5:20pm <-- correct time of my backup
<Name's> backup
I did the restore using the 1st backup. However, the data did not restore and version of iOS remained at 4.2.1
Best Answer
An iOS device's backup typically contains just applications' settings & data. So, if you have just made a backup without saving app or music, you've lost everything. Sorry :'(