Sound but no picture - with codecs installed..

I recently did a reinstall of xp, and have run into problems trying to get videos to play properly.
I get sound but no picture, i have tried installing the k-lite mega codec pack and CCCP but the problem persists. I managed to get some to play by installing the official divx codec, but all the rest still don’t display video. I have the lastest drivers for my video card btw, and windows has updated itself fully.
Thanks to anyone who takes the time to read and reply

Well a codec pack is the lazy person’s solution to playback problems! Each video uses a different codec, and people bundle frequently-used-ones into codec packs, but no codec pack has ALL codecs. (There’s also some dangers of instability with some of them, but I won’t get into that.) The recommended course is usually to download codecs on an as-needed basis, using diagnostic tools like avicodec or gspot. Once you find out the codec the media file uses, you can download and install them. The diagnostic tools can also tell if the file is damaged in any way (truncated, or damaged header for example). If that’s what you have, get back to this thread.

Thanks for the reply.
The thing is, i know that i have the right codec. I’ve just installed power dvd, and when i play back a disc even that gives me sound with no picture. I’ve tried playing avi and .flv files and get the same result, no picture but sound is ok.

Managed to get it working, yay! It wasn’t a codec problem, for some reason catalyst control centre had contrast and saturation set to zero for video playback... no idea why, but it works now so i’m happy.

Thank you Euclid, i ran into the same exact problem and u just solved it for me. Thank you

I ran into this problem after installing a new Radeon HD 4870, and this fixed it! Thanks.

Same problem here and your solution fixed it! In the Catalyst Control Center go to the Avivo Video selection. There you can adjust the Saturnation and Contrast settings back to 100 (custom ?)

i have photos and movie photos stored on my pictures, I have lost the sound on the videos, any help!!!