Is your Nero 8 software not performing backups successfully? You can try downloading and installing a most recent Nero 8 update to try to fix your issue. You will need to supply an email address for those FREE update(s).
Also, make sure you have activated your product via your serial number. Make sure you activate any patents when prompted. Some features in Nero won't work until you activate any patents associated with that particular feature.
You may have to email Nero support if you feel that program is installed correctly and you have it activated as well as all patents activated. The Nero 8 FAQ has a post titled "The patent has been successfully activated, so why can’t I use certain features?" that covers this issue.