In Windows 7, the game still runs after closing it

I have a computer that is running on Windows 7 and it has a problem that I am unable to do away with. I started a particular game and then closed it. But the weird thing is that even after rebooting it, the computer thinks that the game is still running. I don’t understand this. I have tried several things but none of it has solved the problem. I am now desperate for your help.
