Why so laggy?

[3dge]

Your graphics card is just too weak for the game, unfortunately you have already done everything you can. If the game is from steam try a file integrity check in case there are corrupted files causing the lag but I'm certain that this is due to the old graphics card.

As he said, your "graphics card" is just too weak, a integrated graphics card like your isn't really made to handle games. If you want to buy a computer check if it actually has a dedicated GPU, a chipset family is just a graphics card that is basically a part of your motherboard, often used in laptops to preserve space. Sorry for the problems you are having, this is truly a game everybody should get to enjoy!