Match aspect ratio
 

Don't know why but here lately on my video projects it seems i always have to match aspect ratio to get the full screen covered by the video. I converted some qt clips to avi and all of those were too small. There is also some wmv files on another project that this is happening as well. Is there a setting in properties that I need to change? It's just a nuisance.

It's the square vs. rectangular pixels issue.
Pro 9 added a feature to take care of this automatically.
If you have an older version, there are scripts to do this for you.
If yo have any version of Movie Studio, you have to do it one by one as scripts aren't supported.