Windows 7 - Media Player wont play video

Hello people, im new here in the Windows 7 thing, i'm totally amazed about the new OS, but i've had some problems about the WMP, it started cool, when all videos (MP4 included) could be played with WMP, but suddently, after, 3 weeks of usage on the OS, WMP does not plays video anymore, when i open a video on WMP all the playback screen shows black and the only thing i hear is the audio from video.

This issue has given me a lot of problems when using Sony Vegas 8 to edit videos, because now i can't convert videos with vegas and i cant add videos to edit. Also the thing that i can't watch videos on Windows Media Player.

This problem also occurred on my previous Windows 7 instalation (build 7000), problem that i've tried to solve with some codecs, but no good results though. WMP didn't worked at all.

I hope someone could help me because im very nervous, i work on video edition and this is giving me a lot of troubles.

Thanks everybody.

Remove all codecs and codec packs you installed. Test. Remove all 3rd party video players one by one while testing until none.

Install ffdshow. Test. No good, then remove. Try Shark's codec pack.

I didnt installed any codecs, and tried to delete Media Player Clasic, Still, no results, now im going to test ffdshow.

Deleted Media Player Classic, Installed FFDShow
No results at all, now i will try the new K-Lite Codec Pack for Windows 7

I've found something intresting...
My WMP does not work because a registry key is... ''destroyed''??

These days using Windows Live messenger, ive found some, weird things, when i turn the ''Listening to...'' option to show the music i'm hearing the WLM closes itself, i've tried to fix it, and then... VOYLAA

Error on: ''hkey_local_machine\software\microsoft\mediaplayer\uiplugins''
When i try to reach that registry entry, it says like, i dont have permission, but im the admin so i think that this entry is completly broken, even i've tried to delete it, open it on Failsafe, but no results at all.. if someone haves this problem, please help me :S

hello, this is old post, i think i know what happened, and if others will found this thread by internet, here is possible solution: on your video cards app there is option for colors, saturation, gamma, etc. these options are for ur 3D graphics and there is seperated options only for video! possibly in video options section gama is set to zero, so thats y u see black screen on all videos. it was happened to me like 2 years back on windows xp. i have no idea how that happened itself, but it also made me reinstall whole codecs and stuff in first