DVI cables

I am looking into the differences between
DVI-A cables, DVI-D cables and DVI-I cables.

Why would anyone buy a DVI-D cable if a DVI-Integrated cable can transmit Digital or Analog? If you ever wanted to connect a VGA monitor, the DVI-I cable would come in really handy, right?

When using a graphics card capable of DVI-I, how do you specify analog or digital output? I don't think both are available at the same time on the DVI-I port, are they?

This Wikipedia article explains the differences quite well:

http://en.wikipedia.org/wiki/Digital_Visual_Interface

And here is another good article:

http://www.datapro.net/techinfo/dvi_info.html

I agree that there is not a lot of point in buying a DVD-D cable, you may as well always go for a DVI-I. In fact, anything other than a DVI-I will probably be fairly hard to find these days.

You do not need to explicitly set anything, the graphics card will detect whether a digital connection is available and use that if it is. I think there is a signal to both analogue and digital pins all the time, but in practice only one or the other will be connected at the monitor end, so it isn't an issue.