The problem with freezing every 8 seconds I have seen happen for 2 reasons that i can think of.
1) on a laptop this can be caused by not setting the power saving mode to high performance, If it is set to power saver, (by default) it will throttle back the processor to save power even if you are plugged in. You have to set it to high performance.
2) on PC's I have seen it when a usb hub is plugged into a machine and a mouse is hooked into it, everytime you move the mouse it will slow down the video because it is robbing cpu cycles every 1/1000th of a second to scan where the mouse position is or something. If you unplug the hub and just plug the mouse into the machine this stops. Sometimes I can get it to happen with keyboards as well. The one hub that did this was a belkin hub.
As for the multimedia problem, that sounds like an incorrct video driver issue, or not having the motherboard chipset drivers installed.
hope that helps, if I think of anything else Ill post you back
-K