Harmless Risk...????

I have  a disc which contains two risks ,which were detected by SONAR.

Currently I have NIS 2009.Before having NIS 2009 I used to install the disc without any threat notice shown by  Norton,and even when I did not have Norton. 

 

Now, I don't disagree that  the files are risks or Viruses 

the fact is, if they are security threats ,why they did not cause any trouble(it may be smaller or bigger)to my system ?

 

My system was working perfectly in above discussed cases also without showing any sign of misbehaviour or slowdowns.

 

I trust Norton hence I don't believe so..........but are they False Positives ?