HyperSLI is for enabling SLI on motherboards that are not officially Nvidia SLI certified, but otherwise have the capability.
SLI with different cards (this thread) is for enabling SLI in situations where there are different graphics cards, and SLI would not normally be possible with the different cards. It works with cards of the same general architecture.
So, HyperSLI would be used if you have a mobo that supports Crossfire, but isn't SLI certified.
SLI with different cards would be used if you have an SLI-certified mobo and want to SLI, say, a GTX 480 and a GTX 560 Ti.
Both would be used if you don't have an SLI-certified mobo and also have different cards.
EDIT: In the situation you described (non-SLI mobo, 2 identical GPUs) the person should use HyperSLI.
The problem with the X7200 is that it is a notebook - and the BIOS doesn´t support any other cards than the ones they sold with the notebook.
And Hyper SLI alone just does not do it, SLI can´t be enabled, the button just doesn´t show up, although it DOES nvidia SLI with the cards supported...
So it´s a just a whole different thing with laptops, I guess.