Thanks, JimH, but no joy, although Glynor's info re/ffdshow was very helpful. I thinik the problem goes back to a manual "housecleaning" I did on my sys drive a couple weeks back. Since this HP lappy came with pantloads of trialware, I went through and deleted out a lot of stuff I didn't like the sound of, and in the process I guess I deleted some dependencies also.
Currently, both WMP and MC will not play a valid DVD, and both complain about failure to do something with copy protection.
HP has a "quickplay" (that I almost deleted) which will play the DVD just fine.
My current theory: I tried to download Performer right about that time and couldn't get it properly installed, probably due to remnants of Norton AV. I thnk performer and Bill Gates got together on DRM and then their phone call was disconnected, and now nobody can get the DRM thing going, so everything to do with DVD is suspect for MC and WMP.
It doesn't help that I've gone through and deleted or renamed things that sounded like something the RIAA/MPAA might like. I would do a windows rollback but there's too much other good stuff that would go with it.