How do I know if my messed up sims 3 is because of my computer or the actual sims game?

My sims 3 game is all messed up, my character can't have hair, I can't earn money at all, none of the cheats work,and much much more. My laptop is really messed up its battery is ruined so it must be plugged in at all times, and it is ALWAYS telling that its 'Start up disk is full' I really want to buy a new sims 3 because i'm dying to play it but I don't want to waste my money if its my computers fault it is acting up! How do I know which is causing my Sims to malfunction?