Flash video may be a little too much for the webdt depending on how the video was encoded.
Here is a link for the hardware requirements for flash player 11. http://www.adobe.com/products/flashplayer/tech-specs.html
If memory serves the GX has a 400mhz cpu and 256mb of ram. While you are in bios look at the video adapter settings and think about upping the ram to 24mb of shared video memory. It may help some.