cleaning window 7 registry

yes, you can do that, type the command REGEDIT in Run box and click on OK/OPEN, if you get any pop-up box, continue and allow it, you should get the registry editor window now.
Take backup of registry. Click on File> Export and save the backup.
Create a restore point.
Now expand the Hive(folder) HKLM(Local Machine) and expand SOFTWARE, right click on the registry entry of game and delete it. Now you can collapse HLKM
Now expand the Hive(folder) HKCU(Current User) and expand SOFTWARE, right click on the registry entry of game and delete it. Also expand WOWNODE64 and remove any entry for the game.
Once done, close the registry editor.
Furthermore, type the command APPDATA in Run box and it will open a window, open the folder LOCAL and delete the folder of the game, now go back and open ROAMING folder and do the same.
Now open the folder PROGRAM DATA(hidden as system folder) and delete the folder for the game.
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Before you make changes to registry make sure that you know the name of registry entry of the game, do not delete any registry in case of any doubt.

I would be very careful with the registry, one mistake and you have to reinstall. I personally would go with system restore and restore the game. If that does not interest you, download ccleaner and use the registry cleaner. Although registry cleaners are not normally recommended, this one is known to be benign and safe.

RM33 because you asked this question in your post #1.

If so, can I just clean up the registry of the game only?

I would suggest stay out of the registry.

I do agree with richc46 and use a Restore Point.

I'm still trying figure why one would have Microsoft Office and games on the same computer disk.