videos not streaming smoothly--can I find out where the weak link is?

Factual Questions
1

I have a pretty good basic computer* but youtube video clips don’t play properly–they stop every 20 or 30 seconds, wait for about 10 seconds, and then continue playing. So basically, it is impossible (or just incredibly annoying) to watch a simple minute video clip.

Obviously, there is a weak link in the chain between my house and their site. How can I check where the link is? And is there anything I can do about it?

I googled ‘bandwidth test’, and found some sites that gave me results of a speed test, but I don’t know whether this is relevant to my problem, and don’t know what the results mean:

here are 4 results from tests that I clicked on within the last 5 minutes:

at http://www.bandwidthplace.com/
I got results of:
1.36megabits per second
166.22kilobytes per second

at http://www.beelinebandwidthtest.com/
I got results of:
22K/s (176Kbps)

at http://resources.zdnet.co.uk/speedtest/
7816 kbits downloaded in 5.625 sec

Bandwidth — Solve global telecomplexity with an enterprise communications platform
your download speed :1,309.6 / kbps

What does this mean, and where should I be looking for the bottleneck? And if I do find the bottleneck, is there anything I can do to fix it?
*(Pentium 4, broadband modem from my cable TV company, Windows XP, 1000k of Ram, 3 gigahertz)

2

Sometimes, even on a t1 connection, you need to pause the youtube video, and watch the little download bar right under the video.

What is happening to you is that you are watching a video and then it stops to download more.

On short videos, you might get away w/ never pausing the video, but on modest to long ones, even with great download speeds, my dual core processor fresh out of the box with a gig of RAM on an underutilized T1 will need to let the video download before it can be played. Most of the time, j**ust pausing it long enough for the download content to get a head start is enough **-- you don’t need to download the whole thing before watching it…just giving the download a head start.