What is best way to install os update on semi-synced IPhone

[jamesarm97]

My friend has a 3GS and it was synced to his windows computer. The computer later crashed and needed to have windows reloaded. We plugged in the iPhone after restoring a backup of his windows data. I think I got the iTunes database restored. The phone syncs and does a backup but we have everything disabled (music, apps, etc) because it warned about having the apps and setting replaced on the phone. He wants to update to iOS4 but we are not sure if after putting on the update if we can restore everything from a backup. He does not want to loose his settings and data. I remember that even after restoring from a backup it still has to sync the apps and music to put them back on (he does not have much is any music he cares about, just settings and apps). He has MobileMe so email and contacts are not an issue..

Any thoughts?
James

 

[Matthew Yohe]

Right click on the iPhone in the side bar, click backup.
Right click on the iPhone in the side bar, click Transfer Purchases.
Install update.
Restore from Backup.
Let it transfer Apps over.

Only thing you should have to restore is music/videos that were put on there that weren't purchased from iTunes.