Wierd stuttering and playback issues

[TheSaiyan]

I thank god I found this official forum. Now I can finally get help.

Now, ever since I formatted my computer, the media server has been giving a lot of trouble. Before the format, all videos I threw at it, it would devour and then regurgitate it in glorifull amazingness. However now, I seem to be having issues playing a lot of videos. Problems now are that, videos (mostly HD ones) stutter, and I would need to let it buffer, where as before it would play on the fly. I know this because its the exact same video I had before where it used to stream flawlessly. The next problem is that some wont even play at all, whereas it used to play perfectly before, again, different video, but the exact same one i had before (I backed some stuff up so I saved a couple vids). I've tried to tinker with the settings but to no avail. Specs are:

K-lite codec mega pack 4.5.3
AMD Athlon X2 3800+ Dual Core Processor
Nvidia Geforce 8800GT graphics card
2GB of RAM
Windows XP SP3

Any other specs I would be happy to provide.

Debug.log is http://rapidshare.com/files/198183544/debug.log