I've been trying to connect my pc to my Zenith 27" HDTV (model c27v22) via a 15-pin rgb/vga cable. I've tried different resolutions from 640 to 1024. The manual says "set top box to 640x480p." This is apparently for EDTV. Evertime I connect the PC and turn it on, the TV says "PLease connect a valid video format." Any ideas if what I'm trying is even possible? I know I could get a much clearer picture this way rather than using S-video (which works fine). PC in sig.