不爱峰

Normally, contacts are already a part of the backup. Backup ≠ sync. Syncing means syncing with the contacts list on your computer's address book (Mac Address Book, Outlook, etc.). If that contact list is empty, iTunes assumes (wrongly, IMO) that you want the same on your iPhone, and deletes the contacts. Same goes for calendars, although those are not backed up by iTunes. If you have at least one contact/event on your computer and you sync, you get a merge.replace prompt and choosing Merge transfers the contacts from the phone to the computer.

At this point, since your contacts were erased from the phone and you have none on your computer, and you've synced again to overwrite the one backup iTunes keeps, your contacts may be gone.

The one possibility is if you have a previous backup saved on an external drive from the last time you backed up your hard drive. (You do back up regularly, right?!?) If so, you can Restore from that by copying it from the external backup to the proper location on your internal drive, then performing a Restore.

In Vista, the backup is stored at:

C:\Users\user\AppData\Roaming\Apple Computer\MobileSync\Backup