Why no play .avi or .wmv files in my Windows 7 Windows Media Player

VLC Player. Really.

...but more seriously, it sounds like you are missing a codec. Is it *ALL* AVI files that fail to play or just a few specific ones?

I would start by installing the K-Lite Mega Codec Pack. That includes most of the common codecs:

http://codecguide.com/download_mega.htm

@Frosty555

Thank you for responding.

Actually I have VLC player on my machine.  I have several players including Real Player and Quicktime.  I tried them all on a particular .avi file and non of them worked.  WMP worked in that it played the audio of the file, but not the video.  VLC was the best of the players.  It at least showed the video, but it also was in a constant sort of blinking mode.   Big Blinks.  Couldn't get it to stop.  

So, I downloaded the Codec Pack you mentioned and installed it.  Still didn't work.  I rebooted the machine, but I still have the same problems.

Any other suggestions

Additional Information:

It appears this is file specific.  That is, I have discovered I am indeed able to open some .AVI and WMV files.

Does this mean that the ones I am unable to open are simply defective or is it something else?

Request you to check whether you have display drivers correctly installed. Check whether there is any updated version of the drivers available.

Thank you