Suppose I have one the one hand one iTunes library on a PC used to sync Outlook contacts and calendar plus on the other hand one iTunes library on a Mac that syncs music, podcasts, apps, ringtones, etc. Both libraries are based on iTunes 9.0.2.

It turns out that the iTunes library on the PC always tries to sync apps and ringtones as well. Unfortunately, this boils down to deleting apps and ringtones from the iPhone because the apps are not part of the iTunes library on the PC. After unchecking the checkbox to sync apps and ringtones and plugging the iPhone into the Mac the checkbox is also unchecked on the Mac.

It seems as if the settings for syncing apps and ringtones are stored on the iPhone rather than in the particular iTunes library. Whenever syncing apps and ringtones is active on one machine it is also active on the other and vice versa.

How can I make the PC ignore apps and ringtones and only sync contacts and calendar?