Laptop screen when playing not full screen?

When playing sims my laptop screen always has the resolution: 1,024 + 768. I change in game option also always 1600 + 900, but if I save it and reboot then it is small again. Can someone help me with that? Do I have to do something in the normal settings? I'm looking forward to any help, because always having to readjust is annoying in the long run.

What kind of laptop model do you have? How old is your device?

which Sims part is that?