You have a machine that is relatively strong enough to competently perform most ordinary computing functions including good quality display of media from CD/DVD and media files on Hard Drive.
Your machines performance will very likely improve after you complete the Tune-Up Tips listed in your PCPitstop Full Tests Results. By "improve" it is unlikely that you will experience much in the way of "speeding up" of function though that is possibly after reducing the amount of space reserved for System Restore Points, and defragging your seriously fragmented C:\ partition.
It is recommended that you run the native Windows Defragmenting Tool (3) three times in a row to accomplish a good defragmentation. Defragmenting most modern hard drives does very little for "speeding up" performance but may make a significant and noticeable difference in reliable error-free loading and function, especially with regard to resource intensive function like media display and media rendering.
You have a fairly large number of processes and applications that start running when you boot your machine.
You can use the PCPitstop Full Tests Results in the "Windows" section to identify start-up items that are unnecessary and can be disabled via MSCONFIG. In particular, please consider disabling those items that are listed with Purple background on the Windows panel page of your Full Tests results. You can double-click any of those items to receive additional information about the item, its function, and method for disabling the item from Start-up.
You can expect a more significant improvement of machine function after disabling the recommended Purple startup items and you should see a reduction of your CPU load down to (0) zero load, which is what you should expect from a machine with strong resources like your own.
Specific to you problem of pixelated and choppy media viewing.....
You have a variety of VideoDisplay Players.
ViewPoint Media Player
Windows Media Player 11
QuickTime Media Player
VideoLAN VLC media player 0.8.1
and possibly some others embedded in various media rendering utilities you have installed.
It is "OK" to have and use all of those media players, but not necessary.
Some folks prefer the VideoLAN VLC media player because it is open-source, cross-platform compatible, and capable of displaying a wide variety of media formats without the use of additional Codecs.
Your version (VideoLAN VLC media player 0.8.1) is somewhat out-of-date and you may experience better playback/viewing with the more current VLC media player 0.8.6c.
While it is "OK" to have all (5) five of those media player utilities installed, it is not necessary.
Windows Media Player 11 is suitable for playback of most all media formats when Power DVD (you already have this) is installed along with the most recent version of K-lite mega Codec Pack.
Your version of K-Lite Mega Codec Pack 1.71 is significantly out-of-date.
You should consider uninstalling K-lite mega Codec Pack via Control Panel - Add/Remove
Then download and install the current version: K-Lite Mega Codec Pack 3.5.3
K-Lite Mega Codec Pack 3.5.3 incorporates versions of "Real-Alternative" and "QuickTime-Alternative" which provide the same utility as the branded version, while being less resource intensive.
You have a large assortment of video and audio rendering utilities.
It is likely that some of those utilities are trial or demo versions which have already expired.
You should consider Uninstalling any of these utilities that have already expired.
Each one of those rendering utilities may have their own proprietary associated Codecs.
Some of those Codecs may be "conflicting" with the smooth running of media player utilities.
You have Nimo Codecs Pack v4.33 installed.
This is a mildly older version, but may be conflicting with the competent function of Codecs supplied in K-Lite Mega Codec Pack 3.5.3
Please consider uninstalling Nimo Codecs Pack via Control Panel - Add/Remove.
If you consider removing some of the unnecessary media playback and rendering utilities and some of the Codec packs, be sure to use Control Panel - Add/Remove to uninstall them completely and DO NOT try to remove them by a simple Delete, since much of the configuration and file associations can only be removed when competently using the Uninstal function of Control Panel - Add/Remove.
After you have completed the above recommendations, please run a fresh PCPitstop Full Tests and Post the new TechExpress link back here into this thread for additional review and recommendations if necessary.