Movie Library now ONLY displays .AVI file types in WMC7

For some reason, WMC7 has stopped showing any video file EXCEPT for .AVI files. This is irritating as about half of my Movie Library consists of MP4 files. The movies play fine in WMP and also play fine in WMC7(if I right click on the video file and click on Play with WMC7), but the files don't show up in the library. I'm assuming this is some type of registry issue? I found a fix in another forum, and this is what it instructed me to do:

Type "regedit" in the search space right above the "Start" icon.
You need to know the extension of the file e.g.: ".mpg.", "jpg, for jepg", ".mp4"... etc.
Double click "HKEY_CLASSES_ROOT"
Look for the known extension.
Let's say, you want to see picture files on WMC, so scroll down to ".jpg" Right click it and select "New" then "string Value". Name it "Content Type", then right click the new value and select "Modify". Type: "Image/jpeg"
Right click ".jpg" again and select: " New" then "String Value". Rename it: "PerceivedType" (has to be two words together, as I typed it). Right click the new value and select: Modify. Type "Image".

I did this for MP4 video files, and they seemed to solve the problem, and my full movie library was showing in WMC7, however the next time I opened WMC7, it was back to the drawing board. I have 290 video files and only 133 of them show up in the movie library.

No help on this topic? For an additional note, all of my movies are stored on a western digital My Book external hard drive, and all other computers on my Homegroup recognizes and sees the full movie library(in windows media center). I need some help here.