There is the other option of setting up the iPhone manually however you may lose some data when you do this. If you use iCloud for backups etc, then that will help restore your photos and other data. If the computer backup is all you have then, as you know, you will need to restore form that backup file.
Before you do decide to setup the iPhone manually (you may already have at this point), try the restore process again by erasing the contents and settings of your iPhone.
Open Settings ➔ General ➔ Reset ➔ Erase all contents & Settings. This action will erase everything on your iPhone and return it to like new and back to factory settings.
You can then follow the instructions in this guide published by Apple ➔ How restore your iPhone from a computer backup.
Axel F.