With a xbox 360 will you be able to watch HD dvds?
If you wanted to watch HD DVDs on the 360 you would have to buy the extra external HD DVD player. This does not make much sense now because HD DVDs "lost" the format war to Blu Ray.
Can region 1 dvds be played on Xbox 360?
Yes - though depending on where you purchased your Xbox 360, you may or may not be able to do so. Region 1 DVDs are designated to be played primarily in North America (Canada, U.S), U.S. territories, and Bermuda. If you purchased your Xbox 360 in any of these areas, you should be good. If not, you can watch it on your PC.