Is running to slow.

Hi, I am running win.ME and Im not real savy with pcs but I have recently installed norton system works 2003 edition and since then my pc runs very slow and im wondering if it is to much for my system or if i need more memory installed? Ive currently got 576mb of ram but since ive installed this norton version my system performance is way down. It runs in the high 40% range. I had another norton antivirus before but after it ran out i bought this one to update the service and have since startedwith the problem. Any and all help would be apreciated. Ive tried to look for help on the web with no results and just came across your web site so I thought id try and see if anyone here could help.
Thank you.