The things I found I thought had little if anything to do with DRM.

I'd look around bugtraq - e.g. here's a list of threads on [link|http://marc.info/?l=bugtraq&w=2&r=1&s=wmp&q=b|wmp]. AFAIK, most of the windows security issues eventually show up there.

Good luck.

Cheers,
Scott.