Virus or Norton

Two weeks ago I went out and brought norton. Then last week my Microsoft word didn't strat right up instead it took about 10 minutes for it too load. Then I saw that my norton wasn't strating up. So I read a few weeks back that symantec would take up a lot of RAM or process so I unistalled Norton and I am on the verge of returning it. Now today my WinRAR takes 10 min of starting up and Microsoft word scanner tools are taking a long time to strat up. So what should I do.
P.S.- I'm now using Avast trial anti virus nothing came up. And I also use WIN Patrol everything looks clean. And used Spybot and Adaware.

OS: XP
Type of machine: Dell Dimension 4550
Ram: 1GB
CPU: Intel (DOn't know how fast the speed clock thing isn't in properties)

 

I also forgot to add that the clock sometimes pops up when u click the start bar. SOMETIMES thou not all of the time.