Well if the error message says "reinstall microsoft xml core services 4.0" that would be where to start. Go to Add/Remove programs and if microsoft xml core services is there uninstall it. Then go to Windows Update, click on "Custom" and see if microsoft xml core services 4.0 is there, if it is install it.
If not you can get it here:
http://fileforum.betanews.com/detail...es/995451521/1
However you can still run Nero without using Nero Smart Start. Smart Start is just a front end application that starts the other programs. Go to Start > All Programs > Nero and look for the program you want to use, most of the time it's the burning application so depending on which version of Nero you have it would be either Nero Express or Nero Burning ROM. You can start the program from there.