Video problem

My computer is a laptop, but I use it in a docking station, so that I can
have a big (external) monitor, full size keyboard, mouse, etc. Last year
when people would send me a .wmv file attachment (that opened with Windows
Media Player), if the laptop was OUT of the docking station, I got audio and
video. But with the laptop IN the docking station, I only got audio, not
video.

A knowledgeable relative who was visiting at the time, found some sort of
setting and was able to 'fix' it so that I got both audio and video on both
screens. But my computer crashed a couple of months ago and although my
computer man was able to save my data, (including e-mails) he had to
reinstall Windows (XP) and we are gradually reinstalling my various
programs. But I just noticed yesterday (I received another .wmv
attachment) that once again, I am not getting video in such attachments.
I e-mailed said relative, but not being here, he can't remember what he had
done at the time. Any help with this will be greatly appreciated!