Is there anything i could get for my PC that will help it run smoother. Because at top resolution (1440 by 900) it lags a lot and on the lowest resolution it still lags but the lag is on and off. I'll show you my specs.

CPU: AMD Athlon Dual Core Processor 4450e
CPU Speed: 2.3 GHz
RAM: 3.0GB
OS: Windows XP
Graphics Card: ATI Radeon HD 5450 (I got this like 3 days ago just so i can play this)