Pprune Pop,
Earlier versions of Media Player will buffer a larger bit of a clip when there is more memory available. You can change the default buffering here:
Media Player > Tools > Options > Performance Tab > Network Buffering.
The newer versions of Mplayer (10 & 11) are better at streaming. Microsoft.com/mediaplayer.
You Tube is unaffected by media player's idiosyncrasies since it uses Flash player.
Good Luck!