I'm pretty sure you have to- to make sure all you have to do is go to Windows Update and see what it thinks you need. Also it's always a good idea to check for the latest drivers. I'm not sure about Norton Systemworks, however- my experience with it and similar software has always been that they slow down the computer by hogging memory and resources w/o much benefit.
INSTALLING WINDOWS ON TOP OF WINDOWS?
CoolComputing Forum » Microsoft/Windows Software QuestionsI ALMOST ALWAYS INSTALL WINDOWS WITH A CLEAN INSTALL. HOWEVER THERE ARE TIMES
WHEN WINDOWS HAS BEEN CORRUPTED SO BADLY THAT I HAVE HAD TO INSTALL WINDOWS 98SE ON TOP OF
WINDOWS 98SE TO GET TO MY FILES. THE QUESTION IS: DO I NOW HAVE TO RE-INSTALL THE
WINDOWS UPDATES. I DO SEE THAT SOMETIMES I HAVE TO RE-INSTALL SOME DRIVERS AND
RE-INSTALL NORTON SYSTEMWORKS AFTER THIS TYPE OF REPAIR. 
