My Netflix online movies will play only a minute, sometimes five, before it starts to sputter and then stop.?

I don't know what the computer gizmo is called but I do have 503 MB RAM and then, I think it's called a Processor, is 2.38 of something or other. I think it's considered good. I also am always getting in the beginning from Netflix, just before the movie is supposed to start, some text on the red screen telling me my internet connection is slow and their program is adjusting it so as to minimize interruptions. It never works however. Now I can not get the movie, any of them, for more than a minute. I have no idea of what to do about it. If it matters, I have 80 GB hard drive and 50% of it is used. I'd be happy to hear any ideas?