Intel® HD Graphics 4000 actually supports Shader model 5.0 so it should be able to work fine. Furthermore, Maplestory has been tested and determined to be playable using this video controller over Microsoft* Windows* 7.
Please review and follow the steps on this article:
And confirm that you are using the latest video driver, latest BIOS and latest updates for the games you are having issues with.
Then provide the dxdiag report from your system and screenshoots where you see the issue so we can get an idea of what you see.