I know this may be a point of contention with some; if you are looking for a rather inexpensive option and are already looking at a full IP solution, I would recommend GeoVision IP cameras. They come with a disc to load the NVR software. The IP cameras are a little more expensive, but in a 4 channel solution the balance of not having the cost of a capture card works out for the quality of equipment you're getting.
Check out www.usavisionsys.com for details.