Slow Video After IE8 Upgrade

So far I've worked out most of the little bugs since upgrading from IE6 to
IE8. Only problem now is that when I view video in the browser, the audio is
fine, but the video stops and starts and doesn't sych up with the audio. It
only seems to show about 1 out every 5 video frames. This happens in a video
website, and also in Facebook. It was not like that when I had IE6. Video
viewed in browser was viewed perfect before upgrade. I have XP Home with SP3.
I running Intel Celeron 2.00GHZ and I have 768 MB of RAM.
Do I need another RAM updgrade to 1024 MB?
Thanks.
Tom B.