Well, I usually notice this difference when i am playing games. I have an AMD athlon 64 3000+ venice and 1.5 gb of ram. I ussually play WoW and i oftenly go loook up quests. I noticed when i leave the firefox on, the gameplay will start lagging and when i check the task manager, firefox is way up there. When I close it, i resume my smooth gameplay. Is there any tweaks for this?