In order to change the resolution for your game you will need to locate GraphicRules.sgr in C:\Program Files (x86)\EA GAMES\The Sims 2\Mansions and Garden Stuff\TSData\Res\Config. If you have Sims 2 Ultimate Collection the file is in a slightly different place, see here.
It is a simple text file. SAVE the old file first, in case this all goes pearshaped. I do this by simply renaming it to GraphicsRulesOld.Sgr.
The Sims 2 often forces the game to play in only low settings if it can’t recognise a graphics card. By now, it doesn't recognise MOST people's graphics card.
Search for the lines “seti Low 1? “seti Medium 2? and “seti High 3?. These tell the game which default mode to start in and in some cases it will prevent you from changing options in the game. Change “seti Low 1? and “seti Medium 2? to “seti Low 3? “seti Medium 3?. This will tell the game to use the “high” settings within this file.
Now find the phrase “ScreenModeResolution”.
Edit “uintProp maxResWidth” to 1920 and “uintProp maxResHeight” to 1080 in all four sections here.
Save, making sure the file saves as Graphics Rules.sgr and not txt.
Start the game up. More options for screen size should now be available. Select your desired size and hit Apply Settings, and you are now able to play in a larger screen size.
I find the setting 1280 x 1024 works well, in a window, allowing me to see other applications too.
The shadows ingame are clearly not working if you see this.
You can try to turn the shadows off ingame. This might work.
What worked for me was in the graphics rules file turning them ALL off (where they are linked to the different qualities of resolution) - set them all to "false". THEN and only then could I see the Shadows radio buttons in the Screen Options ingame. THEN I could turn it to Medium, which is the recommended option.
It's only possible to edit the Shadows options on a Lot, not in the Neighbourhood Screen.
Sita January 30, 2019