Depends on the card. You see it can only output two displays at a time. Likely the VGA and DVI share the same output, so when you connect the VGA cable your DVI is disabled. The HDMI takes over output 1 as only the first output on Radeon cards outputs video, leaving output 2 for your other connections. It could be that the DVI and HDMI share output 1, in which case you would have to disconnect your HDMI cable to get the DVI to work but usually it's the former mentioned above .
Thanks - looks like your both right - I can't do all three outputs from the ATI Radeon at the same time - only two. My assumption that the DVI was just tapped off the HDMI was wrong - because they have different qualities. i.e- different number of bits for colour.
I've now got the VGA connected to the Benq 22" monitor and the HDMI going to the HDTV - which is an improvement from displaying it ( the VGA) on the HDTV as I was doing before. I'd prefer a DVI connection but I'll accept the VGA.
Next step is to send the HDMI down to the 42" HDTV in the rec room - a distance of 30 ft. Hopefully two 24 SWG HDMI cables with a booster in between will do the trick. Anyone out there know whether there's such a thing as an HDMI splitter. It's not absolutely essential but it would allow me to monitor te HDMI from up here before it goes down there.