I been able to use the same configuration as you want but not with DVI, just with a regular VGA Port on my GeForceFx 5200...i mean... one CRT 15"trought the VGA and one TV NTSC conected trought s-video a the same time...but i have to use the nvtv utility, because i culdn't be able to start the tv output without it.
here is the link to the software:
i hope this help.
P.D. Sorry for my English, it's not my native Languaje.