Hey man I came threw..
Look at classes_root and for each video type the root of each node is empty. Something you've installed had taken out the Content Type and PerceivedType settings.
So to fix use, and save the below as "fix_movie_associations.reg" and run it from the desktop. Now all the media should be playing in WMC and WMP
Save the below into a *.reg file and run it.
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\.asf]
"Content Type"="video/x-ms-asf"
"PerceivedType"="video"
[HKEY_CLASSES_ROOT\.avi]
"Content Type"="video/avi"
"PerceivedType"="video"
[HKEY_CLASSES_ROOT\.divx]
"Content Type"="video/mpeg"
"PerceivedType"="video"
[HKEY_CLASSES_ROOT\.flv]
"PerceivedType"="video"
"Content Type"="video/x-flv"
[HKEY_CLASSES_ROOT\.m4v]
"Content Type"="video/mp4"
"PerceivedType"="video"
[HKEY_CLASSES_ROOT\.mp4]
"Content Type"="video/mp4"
"PerceivedType"="video"
[HKEY_CLASSES_ROOT\.mpe]
"Content Type"="video/mpeg"
"PerceivedType"="video"
[HKEY_CLASSES_ROOT\.mpeg]
"Content Type"="video/mpeg"
"PerceivedType"="video"
[HKEY_CLASSES_ROOT\.mpg]
"Content Type"="video/mpeg"
"PerceivedType"="video"
[HKEY_CLASSES_ROOT\.mov]
"Content Type"="video/quicktime"
"PerceivedType"="video"
[HKEY_CLASSES_ROOT\.MPE]
"Content Type"="video/mpeg"
"PerceivedType"="video"
[HKEY_CLASSES_ROOT\.wmv]
"Content Type"="video/x-ms-wmv"
"PerceivedType"="video"
Please Rep if helped...Top Right Scale of this post..