AAAARGH *kicks youtube*

ARgh arghr argh. I don't know if it's that my computer's getting too old for this or what. Is there a way to forcibly downgrade Youtube videos? Because everything I've been watching for the past week, even if it looks like it's in lower quality, seems to be too high quality to play smoothly. The sound will come through fine but the picture will hang and stick and it doesn't even look good! >.< And I'm on basic DSL, by the way. Especially frustrating because I've been trying to watch vids that have dancing in them.

Suggestions? Halp? o_________o