Most graphic intense games such as The Sims really like to have a dedicated video card. Has someone installed a video card to your system?
To find out how much RAM you have (both video and system), you can d/l
Everest Home.
On the Everest report, click Computer and summary.
Under the motherboard heading, system memory, it will tell you how much system RAM you have installed.
Under display, video adaptor, it will tell you how much video RAM you have, even if it is embedded or on-board.