you may not be able to get the kind of video you want with that equipment. DSL is about 20 times slower than cable and a computer that came with xp on it just doesnt have a lot of horse power.
have you got a phone or tablet that you can use to test whether the video comes in ok on that ? they are going to do it better than an xp computer does. If they work ok through the wifi than the problem is with your computer. While we can clean that up some there is still going to be a limit to how fast it can display it.
have you done a speed test to see if the dsl is giving you the speed that you are paying for ?