.Net framework can be obtained as a download from the microsoft download
center or though windows update.
Whether your game needs it or not it's best to check with the game vendor.
Some programs that need a version of .Net have it on the installation CD.
Note that there are several versions of .Net, and they are not backward
compatible, so some programs need .Net 1.1 and others .Net 2.0, but not
all programs written for 1.1 will work with 2.0
Personally I would say you are better off with out Norton Systemworks, and
unless there is some problem with the system don't rely on it to tell you
some problem exists.