Thanks for the response!
It's just one of those things that make me heave a long sigh. I've had the same OS installation for 7 years now and I've burned through numerous iterations of VLC / MPC / SVP / K-Lite Mega Codec Pack / various other miscellaneous encoders and decoders. I probably need to uninstall everything, clean up the registry and try again. I posted here with hope for a quick easy fix, but I knew it would probably require actual troubleshooting.
Give me a week or so and I'll try to clean up the system and make another installation attempt. If I still have problems, I'll come back here and reply to this thread. Thanks again.