How to make Youtube Faster?

I have an old dell computer however I installed a clean Hard Drive with 7200 RPM. I maxed the computer out with 500mb of ram, and newly installed windows. My computer starts up fast, loads fast. The only problem is online videos like youtube. They load very fast, however the playback is very laggy and slow. Is this a problem with my 64mb Graphics card, or processor? I have good internet. Thanks!