big question and someone eles may have more advice than myself.
I do not have a windows 7 system in front of me but it will depend on what email you are using.
If you are using a web base email like yahoo or gmail than the windows 7 will take care of it.
you must have the proper WMV encoder, you can get this free on the internet, search for a Codec pack for WMV files. \just download and install
Windows media Player than will play it, but you have to link it.
first go to windows explore
options on top
got to file type
find the extention WMV and assign it to windows media player.
should work then