please do the following,
1/ go to control panel and then navigate to add/remove programs. The remove the harr potter game if listed.
2/in the start menu, there is a 'run' command. Click this with mouse and type 'dxdiag'. Run all the tests it offers. These should complete fine.
3/then navigate to accessories in the start menu, and locate system tools. Then select disk cleanup and clean up all your disk(might take a while)
4/Then re-install the game fully(full install)
5/then restart the pc, even though it says it has installed fine, restart anyway.