To BC.com adventureluck!
It is my hope that you will get the answers you need from this forum.
I have not ever used diagnostic cards in my electronics trade so I can not advise you on that topic.
Do you seem to have any problems playing video games on this system?
Try using the directx analysis tool to see if you have a video related problem.
If everything there checks out OK, you may have a ethernet card problem because your speaking here of viewing streaming video from youtube.
See how your frame rates are while playing a graphics intensive video game from a disk or your harddrive.
Or try using 3dmark06 available from this link http://majorgeeks.com/3DMark06_d4935.html
Good luck and please post back your results.
Edited by MrBruce1959, 25 March 2010 - 01:08 AM.