Many readers encounter problems with iTunes 10 asking to synchronize / delete iPhone library when linked to another computer
This tutorial shows How to prevent iTunes 10 from trying to sync / erase iPhone on a different computer
When you sync your iPhone to a computer and have checked the "Manually manage music and videos" option on that computer, you cannot activate this option for other computers ( since iTunes 10.x )
Then, you need to clone the Library Persistend ID for OSX and iTunes 10 as follows:
On the second computer ( where you cannot activate the "Manually manage music and videos" option ):
- Close iTunes
- Locate your iTunes Music folder ( usually My Documents/My Music/iTunes, if not, find the path in iTunes->Edit->Preferences->Advanced )
- Open "iTunes Music Library.xml" (do not confound with "iTunes Library.xml" ) in a text editor such as Notepad ( to access Notepad, type Windows key + R and type notepad or click Start->Programs->Accessories )
- Replace the key under "Library Persistent ID" with the value from the same file of your first computer
- Also replace the path to your Music folder one line above if different from the first computer ( typically when switching from XP to 7 )
- Save
- Open "iTunes Library.itl" in Notepad
- Corrupt it by deleting a few lines and typing some dummy text
- Save
- Open iTunes
iTunes now recognizes the corrupt file and rebuilds your Library with the new persistent ID from the .xml file. After that, you will be able to enable the "Manually manage music and videos" option without being prompted to Erase and Sync your data
Notes & possible issues
iTunes Library.itl is located in the following locations
- Windows XP: \Documents and Settings\[your username]\My Documents\My Music\
- Windows Vista: \Users\[your username]\Music\
- Windows 7: \Users\[your username]\My Music\
- Mac OS X: /Users/[your username]/Music

Mike Johnson
Founder and Editor of sync-iphone.com has a sincere desire to provide readers with honest and useful solutions for their iPhone
More about him on Google+
Note: if you want to Synchronize iPhone with several Computers click here
When you search over the Internet How to synchronize iPhone with multiple iTunes libraries, all you can find are solutions to Synchronize iPhone with several PC
We are looking for just the opposite: Manage several iTunes libraries on a single Computer
Indeed.
What if, within a household, every person wants to keep his / her iTunes library separated from the others'?
More simply, you may want to create an iTunes library for each of your iPod / iPhones and switch between them on the same Computer
The only application we found able to do this is this one
It will allow you to create multiple iTunes libraries on a single computer and keep them separated without any risk of accidental mix-up
Notes & possible issues
- This solution is compatible with all iPhone & iTunes versions
- Once set up, this program allows you to switch between as many iTunes libraries as you want. It's like having several iTunes on one Computer
- Once you created more than one iTunes library on a single Computer, you can Transfer Music from an iPhone to a dedicated iTunes library

Mike Johnson
Founder and Editor of sync-iphone.com has a sincere desire to provide readers with honest and useful solutions for their iPhone
More about him on Google+
Before you start:
- If you are looking for instructions to Transfer iPad to iTunes, please refer to our dedicated post
- Here is How to Synchronize iPhone and iPad, two iPhones, two iPod Touch or two iPads together
- And here is Sync iPhone Calendar with iPad
Below are two other iPhone to iPad synchronizations requested by many readers that we'd also like to show you:
Sync iPhone Apps with iPad
Transferring your iPhone Apps to your iPad couldn't be easier
Start with a backup of your iPhone Apps to iTunes:
- Connect your iPhone to your Computer ( iTunes should open up automatically. If not, launch it from Start->All Programs->iTunes->iTunes )
- Click your iPhone in the "Devices" section on the left
- Click the "Apps" tab
- Check the "Sync Apps" check box
- Select the Apps you want to sync
- Click the "Sync" button in iTunes lower-right corner
Now that your iPhone Apps are transferred to iTunes, you just need to Sync your iPad with iTunes
- Connect your iPad to your Computer
- In iTunes, click your iPad in the "Devices" section on the left
- Click the "Apps" tab
- Check the "Sync Apps" check box
- Select the Apps you want to sync
- Click the "Sync" button in iTunes lower-right corner
Notes & possible issues
- You can of course use this procedure to transfer your Apps the other way round, from iPad to iPhone and from any iPod device to any other
Sync more than one iPod, iPhone or iPad with iTunes - Sync multiple iPhone with one Computer - Sync iPhone plus iPad with iTunes
Note: for instructions on How to Keep iPhone synchronized with multiple iTunes libraries, please refer to our dedicated post
Contrary of what many people believe ( or fear ), there's no problem syncing as many iPod devices to iTunes as you want
- Just connect any device ( iPod, iPhone or iPad ) to your Computer
- In iTunes, click your iPhone or iPad in the "Devices" section on the left
- Use tabs such as "Info" or "Apps" to set up your synchronization settings
- When you are done, click the "Sync" button in iTunes lower-right corner
- Now, connect another iPod, iPhone or iPad and you'll be able to set its sync preferences independantly from the first one. iTunes is able to manage several iPod devices separately without mixing anything up
Notes & possible issues
- If iTunes warns you that your iPhone is linked to another library and asks whether you want to sync /delete it, don't do so, unless your iPhone is empty as this would erase its whole contents
Instead, if one of your iPhones is synced to another computer ( library ), start by preventing iTunes from synchronizing iPhone and then Import iPhone content to iTunes
Then only, you can sync your iPhone with your computer - In case you need to Populate iTunes based on iPhone, please follow our step by step instructions
- To manage two sets of iPhone Contacts and Calendars on a single computer, you need to create two user accounts on your computer

Mike Johnson
Founder and Editor of sync-iphone.com has a sincere desire to provide readers with honest and useful solutions for their iPhone
More about him on Google+