Hi Lemonbunnies, on windows 8 move the cursor to the bottom left of the screen which will show up some tabs, select search which should be the top one. In the search box type dxdiag, and select dxdiag which is a blue icon with a yellow cross in it. Click this icon, this will open a new window. Click on 'Save all information' and save the file to your desktop. Open the the file, copy and paste all the info in it to a reply here, there is a lot of info so worry if it looks too big.
This information will tell us several things including what your processor, ram and graphics card is, and from this we can tell you what you can do to improve your game experience.
The fact that your laptop does only have 4gb ram does indicate that is likely to be low end, and may only have an integrated graphics card which is not good for gaming. The game can only utilise 4gb ram due to its inherent nature as a 32bit engine, but your system is also using ram as well so upgrading to 8gb ram might help but if you have a low end processor and an integrated card it might not be worth spending the money unless upgrading to 8gb ram is fairly cheap. Until we see your dxdiag, we cant really tell, but if you do have a low end processor and integrated graphics it is still possible to play Sims 3 but you may have to put up with base game plus 1 or 2 eps to get it to run decently. You can also lower all the game settings in options as that may help as well.