I just bought a new computer, how can I start syncing with this computer without erasing everything already on my iphone?

Question

I just bought a new computer, how can I start syncing with this computer without erasing everything already on my iphone?
Everytime I try to use the option sync manual it wants me to erase everything.
Please help

Answer 1

The iPhone can be synced to one and only one computer at a time. Before you "marry" it to your new computer, be sure your new computer contains all the old computer's information. When you sync the iPhone to a new computer, it will be erased first. Then, whatever is on your iTunes Library will be synced to the iPhone.
Read: iTunes: How to move your music to a new computer
You can also copy its previous backup from the old computer to the new one, then "restore from backup".
From iTunes: About iOS backups
Where iTunes backups are stored on your computer
The folder where your backup data are stored varies depending on the computer's operating system. Make sure the backup folder is included in your periodic data-backup routine.
iTunes places the backup files in the following places:
Mac: ~/Library/Application Support/MobileSync/Backup/
Windows XP: \Documents and Settings\(username)\Application Data\Apple Computer\MobileSync\Backup\
Note: To quickly access the Application Data folder, click Start, and choose Run. Type %appdata% and click OK.
Windows Vista and Windows 7: \Users\(username)\AppData\Roaming\Apple Computer\MobileSync\Backup\
Note: To quickly access the AppData folder, click Start. In the search bar, type %appdata% and press the Return key.