|Try running the Nero General Clean Tool in Windows 7.|
Go here and click the tab named "Nero General Clean Tool": http://www.nero.com/enu/tools-utili...
Read the instructions under "Please proceed as follows". . or print off the page.
Then click "Download" and run it when it's finished downloading.
When it's finished removing Nero, try upgrading to Windows 8 again.
Incidentally, I hope you've checked that Windows 8 drivers are available for your PC or laptop?