If Nero complains that you have a pirated serial number (which is probably correct), do the following:
Delete the file called NeroPatentActivation.exe from "C:\Program Files\Common Files\Nero\Shared\NL3".
Open Nero Control Center by clicking:
Start->All Programs->Nero 8->Nero Toolkit->Nero ControlCenter
Click on Updates tab on the left panel. Uncheck the box that says: "Check for updates every: XXX days"
Click on License tab on the left panel. Then click on Add and add your serial numbers.
Your Nero 8 should now work and be activated permanently.
If this works for you, or if I missed a step, please let me know thanks!