I did this with keyRemap4macbook on OSX.
Enter alone works as Enter
Enter+Key becomes Ctrl+Key.
How do I do this in Windows?
Go to search by navigating the mouse to the bottom right corner of your windows screen.
In the search box, type Change how your keyboard works, and press enter. It will take you to the search window where you can choose Change how your keyboard works.
Here you can choose the option which you like to change.
The answer from @vembutech unfortunately doesn't work.
i.e. there isn't a settings there which does the trick.
Instead I recommend trying AutoHotKey, following this thread as an example