Streaming Media across multiple subnets

I work for a county library system as an administrator that has 28 branches
in multiple locations within the county with multiple subnets. We have just
acquired office-training videos that we are to make available to the public
and I am looking into the best way to do this. On Friday, I did a test
installation of streaming media server on a 2003 server box but did not have
much time to look at it.
So my question is what would be the best way to make these videos available
on the public PCs all running XP pro across multiple subnets without sapping
all of our bandwidth. I cannot setup a server at each location. The files are
wmv. and quite large.

Thanks in advance for any and all help.