When you install any game it will ask if you want to do a typical install or an advanced one. More often than not the only difference between the two options is that with advanced you can tell it where to install. This won't help much with the games you already have installed but you can always re install them. You can also move where you're Documents folder is by Right clicking it, Properties, Location.

you could try uninstalling them and reinstalling them to your D drive, and of course from now on I think it'd be a good idea to use your D drive for storage.

It is not advisable to just physically move a program from one hard drive to another. There are a lot references to where the program is installed on the computer and you cannnot update those references manually. If you want move a program your should first uninstall it and then reinstall it on a difference hard drive.
It is better if you do it with someone knowledgeable around.