Video streaming slow to start on Vista

I purchased an Inspiron 530S with 3 mg memory and Vista.  When I try to do video streaming (like from a website such as youtube) the video will not start right away.  I had a Dell dimension running XP and had no problem with video streaming.  I tried a test with both computers connected to my ISP cable broadband connection, by selecting the same video on both and clicking the start button at the same time.  The old computer with XP and only 512 kb memory, started the video playing in about 3 seconds. While the Inspiron running Vista just sat there with the little circle in the middle of the video screen turning round and round for an additional 30 seconds before the video starts.  It does this on every video I try to play.  Also some of the videos will stop and buffer in the middle, which did not happen near as much with the old Dell Dimension.  Does anyone know if this is a problem with Vista or is it my new Dell Inspiron with some sort of video setting not right?  PS: I even tried this same test with my toshiba laptop (running XP, with 1.5 mg memory) and it started streaming fine also.

Thanks in advance for any help !