streaming video

I have an issue with streaming hi res video on hulu. On standard res... no problem. However when I switch to hi res, the video was constantly pausing and starting again... like it was buffering. Now I have a good internet speed. 16meg down 2 meg up. I updated my video drivers and that did make a noticeable improvement. Now the picture just seems to be slightly off... like a low frame rate perhaps... not as smooth as it should be in playback. This is an old computer so perhaps the hardware is not up to the task. I am running a 2.5gig pentium 4 with 1 gig memory on windows xp and the video card is a radeon 9800 pro. Do I need a faster machine for streaming hi res video or is there another approach I can take to solve this problem.