video stutter home pc issues

English is not my language, so excuse my mistakes.
For a long time now I have been displeased with my HD experience. The problem is a very noticeable stutter on any video that I play from my home PC. Very persistent and annoying since I tried a lots of tweaks an options. It's on every video file regardless of video container or codec. I tried every video player known out there - same thing. I changed OS from Win7 to Win Vista to Win Xp - problem remains. Video is choppy at all times, but most visible at the panoramic views when the camera pans slowly side to side.
Here is what I use for my home cinema - Intel 2,4 I think based PC with 4 gigs Ram, Nvidia 9800 GT GPU, running Win 7, playing mostly 4, 6 to 11 GB mkv (720p 1080p) files with WMP (with CCCP or Klite codecs) or VLC. Using an HDMI to connect to a Sony Bravia 40W2000 (100 Hz). Sound comes out from Asus ext. card trough optical cable and into Sony home entertainment system.
Please don't recommend me to update my drivers, or change my codec pack or try your favorite player (redundant) I HAVE DONE ALL THAT MANY MANY TIMES.
My bet is the video card does not put out all of the frames that are actually in the video files. It feels like I'm watching at 20 frames per second (Wait - NO! I just checked on Youtube fro a 20 fps video - mine is way worst!). TV checks out because I have HDTV SAT/PS3 bluray and everything there is smooth. Only occasional tears appear all the same from PC games, PS3, and fast movements in movies. Reality sucks!
I just want a smooth playback like every poor schmuck out there.

Hi, everyone
I'm from Bulgaria Europe, so - 50Hz at PAL. I know most of the video is 23.9 fps at 60Hz which sucks for us. I assume 120 Hz Tv or monitor would do better, correct me if I'm wrong. But also the conversion the TV uses to display everything properly should not cause that much stutter (although adding frames does not cover for the missing ones). The PC monitor is at 60Hz and it displays the same problem.
I believe the GPU has options from 1920x1080p@60fps for the second monitor(the Sony) down so I keep it at native 1920x1080p@50fps. But I have tried everything to even match the TV frequency to that of the video.
I noticed that my sat receiver has 1920x1080i@60fps and 1920x1080i@50fps as maximum, but when I use 60 Hz the picture flashes rapidly (subtitles, anything white) and smudges a little. At 50 Hz it normalizes so I presume it's better for a 100Hz Tv.
What would be the best way to compare the video stats of the file itself with the signal send after the GPU has processed it? And a way to monitor the work of the GPU during the processing?
Thanks.
I have lots of NVIDIA drivers and yes I have MPC-HC.

So you're saying video is displayed at 60Hz on both display and the TV? Nvidia fault maybe? I'll try the CTRL+J on the MPC-HC, but I'm guessing that would be the feed that the player is receiving regardless of its position (on splitscreen Sony/Asus). I'll give some stats tomorrow morning. It's now 12:12 am here.

Major error on my side!
I don't see 100 Hz for this TV anywhere. I was duped when I bought it. Always thought it was 100Hz, and now I only found one place where it sais 50Hz - at Amazon. I could swear it was promoted as 100 Hz Tv at different sites back when it was released.
That aside I can't turn on this CTRL+J function on the MPC-HC. Nothing happens. What is suppose to show, what is the name of the function, is there another way to turn it on, is there another program that can do it?

Still nothing!
Output is in playback options - there I can only change the desired render. Even when I change something and click apply, nothing visible happens. I downloaded madVR and installed it, but not sure if MPC used it since, well,.. nothing happens when I change something. Still no CTRL+J function! Version of MPC is 1.6.1.4170, I see there is a newer version - 1.6.1.4235, but I don't think it will be that different. Mine came with the codec pack - not sure what will happen if I replace it.
Back to the main point - how to see the GPU video output to compare with video file and see if GPU settings are true (correct)?

Just checked how CTRL-J works on my laptop with MPC v 1.5.3.3819. There was no frames dropped field. Frustrated.
What the hell does my PC wants? Kill-mode.

Thinking of an upgrade.cat falling asleeeppnmy keyborad...llogoff.