Thanks for the replies guys.
My mistake, it's an HVR not an NVR.
Instead of waiting for the adapter you linked or paying $8+ for one from a local store I ended up stripping an old RCA cable and connecting it to the BNC connector, ugly but it worked, as do the cameras.
Why do you say to keep the DVR separate from my home server? The plan was to have it record to its own HDD.
So since the cameras work it must the something with the card/software it came with.
The card shows up as "JVSC890 Device" under "Sound, video and game controllers" in Device Manager. This makes me think that the driver installed correctly and it's the software that it came with that's bad.
Can anyone recommend some software (preferably open source or something that has a freeware/trial version) that might work with this card?
Thanks again