Vista backup of recorded tv (dvr-ms files)

I'm new to Vista and VMC. I'm trying to do the right thing and back up my
documents using Vista backup. I thought I was going along smoothly until I
checked the backups and was shocked to see that my recorded TV shows were not
included in the backup. I haven't been able to find much on this issue with
either Google or searching these forums. Can anyone tell me how to get these
files included in the backup?

Vista Home Premium SP1, patched to date. Plenty of HD space.