Windows 7 - Vertical bars on sides of 16:9 picture?

I got a new windows 7 premium 64 bit laptop. So far I just downloaded divx preview and AC3. When playing some of my 720p mkv's in WMC/WMP there is vertical black bars on the edge of both sides of image. The picture is being squished towrards the middle by black bars. I can play these videos fine using VLC media player and the movie takes up the whole screen. How can I make wmp/wmc stop doing unnessessary cropping! I don't know why but it only does it on some of my movies and not others

Welcome leif, These are the settings I'm using and it fits my screen. Might help you out.

when you say you downloaded AC3, what do you mean exactly? WMP/WMC has built-in support for the AC3/A52 codec, you shouldn't need to d/l an ac3 codec...

Your video settings look the same as mine. I have noticed under file/properties in wmp settings, the squished vids will say Aspect ratio: 10:11 actual, 1.61:1 displayed, while the vids that play correctly say 1:1 actual, 1.78:1 displayed under aspect ratio. Is this a clue to my problem? I know all these vids I''m trying are 720p mkv's.

Regarding AC3, I downloaded that for audio. No mkv videos would even play before I downloaded that.

since they ALL play correctly in VLC, I don't know what the problem could be... I'm curious to know as well.

Is it my divx preview. Is that what wmp uses to watch mkv's? What should I do?

Are you using a codec pack? Sharks codec pack will let you play just about everything in WMP.
Shark007.net - Windows 7 Codecs - WMP12 Codecs

Yeah I'm about to give it a shot. I havn't been able to get spdif 5.1 so far using divx preview/AC3/wmp. Hopefully I'll be able to with shark. I suspect it's divx preview thats giving me black bars on some of my shows. But will shark (or anything else for that matter) be able to do hardware acceleration like divx preview?

The black bars appear when the aspect ratio of the video is not the same as the current aspect ratio set in WMC for your display/TV.

Have you tried the zoom feature? It appears upon right clicking on the video or live tv currently playing. Zoom 2-4 may remove the upper/lower or left/right bars. Video quality/performance may suffer on lower end equipment as a result or you may choose to encode your videos in a better format.

It appears to be a bug with WMC since I'm certain the offending vids are 16:9 but being artificially cropped. I found others here at AVS forum similarily effected:
small black bars on side when watching 16:9 in media center (TV or movie) - AVS Forum