If you synced your contacts with contacts from iTunes with Windows adress books and your contact list is now full of files with all the contacts' email addresses, here you will find out how to delete your address book at a glance.
The first way you can delete all contacts on iphone is to create two empty text files on your desktop and rename them to AddressBookImage.sqlitedb and AddressBook.sqlitedb and copy/overwrite these files into the folder "/var/root/Library/AddressBook" , using "iBrickr", which will empty your contacts list, knowing that all the contact are stored in those files. All the changes will occurr after you restart your iPhone.
Another method is to go in iTunes menu, and in Edit section click on Preferences, in the window that opens up click on the last tab which is "Synching", and press the button with "Reset Sync History". This will resync your iPhone as it will delete all the history. Be careful to check "Replace Information on this iPhone" for Contacts checked. This should work and all the Windows email addresses should disappear.
An alternative method is to create an empty windows identity (for the windows address book synchronization). For this, do the following:
On your PC type in wab.exe. This brings up the Windows Address Book.
File->Switch Identities
Click on Manage Identites->New button. Give it a name e.g. EmptyAddBook. You should get a prompt for switching to the new EmptyAddrBook identity. Choose Yes.
In iTunes->Info tab, choose to sync with Windows Address Book.
In iTunes make sure the Advanced tab has Replace Contacts checked.
The next sync to your iPhone should clear out all the contacts.
You can choose any of these three metods, and see which is the easiest one for you and use it to clean your iPhone address book and delete all contacts on iphone.
Fabio S., on February 14, 2010
Thanks a million ! Saved my life :-)