NTSC/PAL Weather Cam

I’m looking for suggestions. My WD network cam has died :x and I have several good surveillence cameras that I could use but they produce an NTSC signal. I need a capture device/software that can take that signal on a scheduled basis and save a jpg or gif snap shot that WD can pick up and place on my weather page. I’ve looked at allot of capture cards, even have one, but none make that jump from a NTSC signal to a jpg file for a snap shot, automatically. I don’t want to do anything fancy like stream live or anything just a snapshot every 15 minutes or so but all I have at the back of the computer is a NTSC signal.

Any suggestions??

There is a bit of software called Active Webcam that i think might help
you can get a demo version here