Video playback issues in Windows 7 but not Windows XP

We have created a sample version of an experiment that contains videos (WMV files). When running the experiment in Windows XP, the videos always appear correctly on screen. However, when running the experiment in Windows 7, although the videos usually appear correctly, in some cases they are too small, are cut in half with only the top part showing, etc. These errors appear to be random, but do persist over time. Is there anything that can be done to remedy this situation?

Narges--did you ever find a solution for this? I know a number of users found that upgrading to v2010.3 or v2012 helped with these types of video issues when using MediaLab on Windows 7. And that it seemed even better when upgrading to version 12 of the Windows Media Player. Just curious.