Stuttering game and video play back.

I'm having an issue with my NP5793 Sager. It has the T9300, 8800GTX, 4GB 800MHz, 7200RPM drive, 1920x1200 screen, etc. Running Windows 7 Pro x64

When I play videos or games it stutters. About everything second or so it skips a frame or two. It does it with all videos including 480p to 1080p. It also does it with all games in all settings, high or low. L4D2 running 1680x1050 with medium settings gets a pretty constant 70 to 80 fps with no zombies on screen and it still does it then. In Portal 2 it does it the same although it also has sound glitches at the exact time it freezes on screen.

I've got all the latest drivers from Sager/Clevo. I've also looked at later model laptops running similar hardware on the Sager and Clevo sites and downloaded their drivers. I just recently reinstalled Windows 7, still doing it. I am now running the latest nvidia drivers from the nvidia site. I've also tried some off Laptop2Go website. So far nothing has change it (made it worse or better). I've tried running the screen in 61hz and 60hz. Run with no antivirus, run with antivirus, run with antivirus disabled. The list of things I have tried goes on!

It is bad enough that I don't enjoy watching movies on the laptop due to the stuttering. It seems to happen at a fairly predictable rate, almost like it has something to do with a clock speed...

Any thoughts?

Hopefully you can see it on this video I took with my digital camera. I didn't want to do screen capture as I thought that might affect the video anyhow.

http://www.youtube.com/watch?v=zm-ZQ_y8gq0

Thank you.

But Portal was in single player, same with locally hosted L4D2 games.. And the movies were on my hard drive. And it should be able to play a 630x350 odd resolution video without stuttering off the hard drive. It is an old laptop now but not that crap.

Happened on brand new install of Windows. As in format. Even used a different windows 7 disk this time as I lost mine. I've run Malwarebytes, Avast. Defrag shouldn't have an effect because it happens on all content and also a fresh install pretty much defrags the drive. But I will run it anywho and let you know. I have had this issue for well over a year. But now I am wanting to use my computer to play movies and I can't bare the stuttering.

It does it in VLC and Windows Media Player to every video I have opened on this computer. It also does it in YouTube. Always the same timing between stops. It does it in every game I have played also. I stopped playing games ages ago and didn't want stuff on this computer much so that is why I haven't tried hard to find a solution until now. Also it seemed really bad when playing Portal 2 the other week and it bothered me so I decided to put some effort in to try and find the reason behind it. I just finished defrag and played a video, still happening.

EDIT:
Oh just to add I just tried a DVD and it's the same with playing DVDs too.

This sounds very similar to my issue
http://forums.techguy.org/windows-xp/612476-strange-windows-stuttering-briefly-every.html

Wondering now if it has something to do with Windows's power management on my laptop? Going to go look and see what I can find

Is there a particular version I should get, or just that 260.99 beta?

DMA is enabled all round.

I installed 260.99 beta drivers by going into safe mode first and uninstalling plus running Driver Sweeper and CClean. Still the same, but no surprise there as it happened on the old 160 drivers I got from Sagers website and the 19X driver I also have which I got from somewhere. But I had to uninstall the 260.99 as it randomly turned my display off without anyway except turning the computer off to get it to come back on again. So I am back with the nVidia supplied 270.x driver I have.

I have found that I have a constant 3 to 6 % used on my CPU by "System Interrupts"...?

I just tried playing a video under safe mode and it only plays at 10 to 15 fps so it is too hard to see if it is doing it while playing video in safe mode.
I'm thinking I might try installing Windows XP or Vista on an external drive and seeing if it still does it once booted into a different version of Windows...

Hmm, apparently I cannot install Windows on a USB drive.

I think I may have found it though. I uninstalled the video drivers and installed the ones off the original driver disc that I found the other week. It doesn't appear to be doing it now! So it didn't work with 197.16 or 270.61 or those MobileForce 260.99's. But I currently have Sager supplied 187.62 and it appears to be working. I'll let you know how it goes.