All newer dreams don't use a MPEG-2 codec anymore , and later versions of
windows don't include it
So like Dude said install the MPEG-2 codec and your dream should play back
if you didn't make another error , like your video conversion to wmv .
AVI format would be better as it uses just 1/2 the CPU usage as does wmv format.
Some converters are better than others.
As a Dream Maker, I kind of seen a little of everything involving dreams ..