Then go to C:\windows and look for the folder erdnt and make sure your back ups are present. If you did two backups, you will see two folders.
If they are there, go ahead and uninstall Nero through Add/Remove programs.
Next, do a search of your root drive (c:) for any instances of Nero and delete them. You may have to set your folder options to unhide system files so the search will look in the system folders.
PLEASE BE VERY CAREFUL WHEN DOING THE FOLLOWING STEPS. ONE ERROR CAN CAUSE YOUR MACHINE TO BECOME UNBOOTABLE. DO NOT DELETE ANYTHING THAT DOES NOT CONTAIN REFERENCES TO NERO.
Next go to Start/Run.. type in regedit
In the Registry Editor window, click once on MyComputer to select/highlight it. Then go to the menu and click on Edit and choose Find from the menu.
In the Find box, type in Nero, ensure all options are checked, then click Find next
The registry will then be searched and will stop on the first nero instance. The instance will be highlighted. Verify that the instance refers to NERO. Be careful it is not a partial result that the search has found. Meaning the registry search may also find portions of a reference that contains the letters "n e r o". For example, the word onerous contain the letters "n e r o" and the registry seach will stop on it. You have to be careful not to delete partial hits! If you are confident the instance belongs to Nero, then you can delete it.
To find the next instance, hit the F3 key, and the search will continue.
Go through the entire registry and verify/delete all Nero instances until the search flags that no more instances can be found... then exit the registy and restart your computer.
Hopefully, you didn't delete something you weren't supposed to delete!
After restart, try reinstalling Nero again and hopefully you don't end up with the same problem.
You have to decide if you want to try this. It's always scary for me when I give instructions on editing the registry... I would much rather just do it myself! Good luck.