dynamixx

I have recently set up a basic CCTV system consisting of a wireless camera and DVR card linked to my existing, non-standalone PC. I am looking to upgrade the default software that came with the DVR card, and was wondering if anyone had any recommendations based on this admittedly limited information? Ideally, I am after recording software that isn't invasive and runs in the background, or could even run hidden, while using the PC for other tasks, and can record video to a specific drive (a USB stick or external hard drive for example). Bearing in mind the simple nature of my set up, is there worthwhile freeware that could be considered? Any help appreciated.