Your computer may not be 'beefy' enough to handle some of the games. If you have 6GB or under of usable RAM, chances are not all modern games are going to work without lag or memory problems like you experience.
I'm afraid you'll have to upgrade your current PC/Mac, or purchase a new one. (8GB of RAM should handle most games.)
I know its a lot of money just to play a game, and you may not be able to convince your parents to buy it. I'm afraid that's the harsh truth. No beefy computer - no beefy games.
Sorry I couldn't be of further assistance.
~George |