im assuming youre running vista 64? i ask because people have bought 8gig ram for standard xp before not knowing it does no good.
that sounds exactly like my comp and i have no problems running 5. i dont think you need to upgrade to i7 unless your processor is bad. in theory you should be runnin smooth. actually id think you stole my rig if i wasnt typing on it right now maybe you have a virus or spyware or somethign.