Right before getting wracked with a massive head cold, I was trying to solve the NMV file puzzle. Well, I'm happy to say … it's solved.
I managed to track down the company that purchased the very old CCTV business. The card/software, RConTech DVR, was developed for Win95 / Win98. It was discontinued around 2004 and finally went out of support in 2009.
The DVR saves the files in a proprietary format. When attempting to back-up, you're given the usual two choices - out to AVI or out to a "native file" type. In this case, the NMV file is a transcoded copy of the original. The software allows you to choose the compression type for its AVI export, but not the NMV.
So, running in compatibility mode as an administrator, the program is fairly stable. To get there, right click on the program's icon and then click on the Compatibility tab. Select the version of Windows that you need - in this case Win98 was stable enough.