Question : Problem: Need to sync purchased applications without over-writing other apps already on the iPod Touch

Strange situation - I have a "loaner" iPod touch with a bunch of purchased apps on it that I do not want to lose. I can't transfer them to my PC because I don't have rights to them - which is fine.

I've purchased a bunch of other apps through the iTunes store on my PC and now I want to get those new apps onto my iPod. Unlike music, you can't drag and drop apps onto your iPod when you have "manually manage" turned on.

When I go to the apps tab I see some greyed-out options like "sync selected applications" and then a list of the apps on my PC that I can sync. But those buttons are greyed-out. I need to turn on the "Sync Applications" checkbox first.

But when I do that I get a really scary warning saying that all my apps on the iPod will be replaced with the ones in  my library - not at all what I want to do!

How do you just copy applications that you purchased in your iTunes on a PC to your iPod without over-writing existing applications on the iPod that are not in your iTunes on the PC?

Answer : Problem: Need to sync purchased applications without over-writing other apps already on the iPod Touch

Unless you authorize the account of the person that you are borrowing the iPod touch from on your local iTunes and do the "Transfer Purchases" then you wont be able to keep the apps on the iPod Touch. My recommendation would be to reformat the iPod and load your content on it. When you want to give it back all they have to do is reformat it again and it will put their apps and music back on.