Do the following & you'll be OK since you've moved your itunes library:
First, disable auto sync when an ipod/iphone is connected, under preferences in itunes, which in windows is in the edit menu.
Connect your phone, DO NOT SYNC.
Next, go up to Store>Authorize this computer.
Next, File>Transfer Purchases.
Next, make sure you have at least one contact & one event in whatever supported program you use for that purpose. They can be fake, it doesn't matter.
Right click the phone in the device pane & select "Reset Warnings".
Next, right click again & select BACKUP.
Next, restore your phone from the backup you just made.
This must be followed by a sync to restore your itunes content. Which is selected from the various tabs. You should get a prompt regarding your contacts & calendar asking to "merge" or "replace", when you sync. Select "merge"
This is what's included in the backup you'll make & restore from:
http://support.apple.com/kb/HT1766
This is how to restore from that backup, as already referenced, when prompted to create another backup before you restore, decline as we will use the backup we made when we started:
http://support.apple.com/kb/HT1414