with blender when i select HD, is all that changes the size/diemnsions of the picture?

What exactly is your question? HD is simply a giant resolution. If you mistook it to mean hard drive then to save you can press f3 after rendering while hovering over the largest panel to save the image to disk or for animations set the render directory under the render options.

“HD is simply a giant resolution.”

well it took a day and a half to render the 300 frame file. 1.8GB
very sharp picture, but windows media player does not like it.
it runs v e r y s l o o o o w l y !

You probably want to export it to a lower-res to share or watch (if your computer can’t handle it). It is good to have HD footage because you can export down to any level. Are you planning on showing this animation? What is it?

no - we gave our TV away, and now the new ones are HD 1080.
so i wondered what was involved in making blender HD videos.
i will try and use pinnacle to put it on a DVD and play it on the TV. (our ancient tiny non HD!)
UPDATE. Old TV did not understand HD.
But did get the blender HD to run on a DVD NOT set to HD to run on TV
(and it is a different connection from the DVD player to the TV for HD)