unable to preview movies
 

hey! i seem to be missing a codec or 2, but there are quite a few in my pc. "web help" doesn't help at all. i am unable to view some movies and clips. but there are a few i can preview. mp4 is giving me a problem, but some avi are giving me hell too. any help? ive given up.:PEACE:

Be very careful when opening files with strange file extensions.
They could easily be viruses or trojans masking as legitimate files.

your reply didn't help, but thanks anyway. the only files i download are the most common......avi and mpegs. but ive never had this trouble before. i even have ffdshow, and cannot preview many clips or movies. i have to wait until it is downloaded completely, but i don't want to download bogus bootleg movies.it's a waste of time.