You shouldn't need to run new coax unless what is in the walls is either very old or damaged.
Your old TV will still work fine, it just won't have any benefit from HD.
We're thinking of making the switch over to HDTV (Wow's Ultra), and few questions came up that we couldn't clear with Mr. Google. We have two HD monitors and an older tube TV, and mostly want the record/playback versatility and extra channel selections.
Do they need to string all new cable from the pole into and throughout the house, or is the magic in the converter box and HDMI cable to the TV only? What would the optimum setup be?
One of our TVs is the older style analog tube. Will the picture be utter crap, or we just won't see the advantage of the HD on this particular set? In some short time we'll have the set upgraded, but not for a little bit yet.
Anything else to be aware of?
"Giving money and power to government is like giving whiskey and car keys to teenage boys." -P.J. O'Rourke