so I can't ATM test on my running OS or in my Virtual-Machine-XP-OS "test" install so I can't install K-Lite to see what your problem is. Can you say which K-Lite package you installed? It specifically states different packages install different sets of Codecs, so your request is HUGE (kind of). Apparently, since it doesn't know which Player is to use the Codecs you must "roll your own" depending on which Player you want to use.There is a Codec Tweak Tool that may or may not help. I appreciate your reply but Can any one state, how to associate video formats like ( mp4 , 3gp ) with my wmp using any script/registry?