Windows Media Oddity

Hello, I have had an oddity with windows media player 11 since i clean
installed windows vista. When i view online videos and streaming content,
the video seems to start ahead of the audio and then the audio starts
normally a few seconds later, causing the video to slow down and catch up.
This happens with any website that uses windows media player for video and i
have tried everything i can think of to deal with it. Also, when listening to
audio that i've ripped from CDs in WM11, near the end of a track, the sound
gets choppy, then fixes itself and then at the end, goes to the next song
down the line (as normal). Any clues? I have had everything updated when i
was using XP and was also using WMP11 and never had these issues. Thanks!

Intel Pentium D, 3.0
1 Gig RAM
PNY Nvidia 6600 256MB