"Windows Media Player cannot play this DVD because there is a problem with digital copy protection between your DVD drive, decoder, and video card."
I read every post here about this specific error. The "help" was invariably "Use another DVD player application." AKA "Ditch WMP."
Someone has to have solved this here. The smart people density on SevenForums is greater than almost anywhere else on the 'net

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I've read that VMware player can cause it but there's no vmware tasks running when I get the error. Some folks have cited HDCP but I swear DVD playback worked before using this exact same hardware combination. Is there some log file or diagnostic program/mode that can give me any more information?
I'm currently installing a fresh copy of 7 32-bit into Windows Virtual PC to try that out...