Anti-Virus Software

I am a novice with PCs… and am having a problem with my Anti-virus software. I didn’t know I had a software program on my new pc when I purchased it. I believe it is McAfee. Before I knew it was on the pc I loaded Nortons Anti-virus 2002. Now the two seem to be conflicting. Should this happen? Do the two not work together? Could I have caused a problem loading the 2nd software pkg? Do I need to delete one? Please help.