The Sims 2 resolution stuck on 800 x 600.

Hi, I bought The Sims 2 on disc. I have installed it fine, but the resolution is stuck as 800 x 600. There is no option to change it. I have tried editing the game files like people have suggested for the ultimate collection but I can't save the file once I edit it. So that option doesn't work for me.

I've also tried talking to someone at EA support about getting the ultimate collection but they told me they don't give it out anymore.
I don't want to play the game in low resolution as it looks bad.

Am I doing something wrong? Why can't I edit the game files like everyone else can? I can't delete them either...

Please help?

I have Windows 10.