I know it may seem like a PITA right now, but there is a reason why it's a good idea to use Clean Tools after Add/Remove programs and before installing a new version of Nero. There are many different versions of Nero and the registry is mighty complicated.
Sometimes you can get away with just installing new versions over old programs, but an uninstall first and possibly registry cleaning can be a good thing. I actually will search the registry for a few keys words before installing some new software like virus scanners, video drivers and stuff like that.
SKAARJMASTERDUO: WinXPSP3,C2D E8600,Gigabyte EP45-UD3P,4GB RAM,Nvidia GTX-280,Pioneer DVR-216D,BenQ DW1655,Asus E818A3T.
DRAGONSLAYER (bye): WinXPSP3,P4 3.2,Asus P4800-Deluxe,3GB RAM,Radeon 9800Pro 256MB,LG GH22LP20,Asus E616P3,Lite-On LTR-52327S.