Mov files tend to be porn/spam. I stick with mpg and avi files.
It's probably a codec problem.
Free-Codecs.com : Download YV12 QuickTime Codec 1.0a2 : YV12 QuickTime Codec, very useful for developing image processing or compression/decompression software Apple - QuickTime - Technologies - H.264 Final Builds Site
For WMP,
K-Litecode Codec Pack gets recommended a lot. I use
XP Codec Pack 2.0.6 and rarely have any trouble playing a file. Though I don't d/load mov files so I don't know if these will help.
VLC should play it, it plays just about everything. The codecs are already built in:
VLC media player.
More info here:
CODECs list for Movies /Alternate players / Video help forums