cannot play DVDs in Vista Ultimate

[soydios]

I am unable to play DVDs in Vista Ultimate x64, no matter what application I use. I have Roxio Easy Media Creator Suite 9 installed for the myriad of things it does. In Windows Media Player, it tells me this:
"Windows Media Player cannot play this DVD because there is a problem with digital copy protection between your DVD drive, decoder, and video card. Try installing an updated driver for your video card."
I have the Catalyst 7.5 drivers for my X1900XT, and my NEC ND-3550A DVD drive is set to Region 1. Neither my video card nor my monitor are HDCP-compatible.
I've tried installing the DVD-related codecs and the Media Player Classic from the KLite codec pack, but it gives the error "DVD: Copy-Protect Fail."

I have two theories about why it isn't working:
1.) Windows Vista won't play DVDs, even pre-HDCP ones, over an unencrypted DVI link, which would blow if this is the case. Or...
2.) When I installed Roxio Easy Media Creator Suite 9, it screwed with my DVD decoder.

If anyone has any input on my situation, I would greatly appreciate it.

 

[Synomenon]

If your NEC drive has RPC1 firmware, WMP11 will spit that message out at you. You'll need to flash your NEC with non-RPC1 firmware.

 

[soydios]

I never had Region-Free firmware installed. I just flashed from firmware v1.05 to v1.07, and still no dice.

 

[tw1164]

DVDs shouldn't need HDCP, that's for BR & HDDVD

try to open the dvd using VLC

 

[corkyg]

I have two systems with Vista Ultimate - and have seen no problem with DVDs. I have Roxio EMC9 installed on both, but it is not part of the equation. I use Power DVD 7 and also WMP11. Both work.

Are your DVDs originals or copies?