"HD" means "High Definition", as opposed to "SD" which means "Standard Definition." SD equates to a usable resolution of around 640x480 (although its usable bandwidth can actually handle higher, but is this way due to blanking...remember, this was designed for CRTs, not TFTs). High Definition means anything beyond Standard Definition. And no, HD does not mean digital, and can also be analog (component video is analog). I think the problem is that someone is confusing the capabilities of the "VGA Cable" versus the IBM definition of "VGA." In that sense, yes, the IBM definition of "VGA" is not HD, since it's only 256 colours at 720x400...but I think everyone here should know the context.
However, to answer someone's question about what monitor doesn't have a VGA input...well, the Dell FPW3007 actually does not have VGA input. It only has DVI. However, I believe the DVI to VGA adaptor you get from some video cards is capable of converting the the physical layout from VGA to DVI. I think most of these adaptors that come with the video cards are male DVI and female VGA. So, for those of you lucky enough to own a 3007, you can probably plug the converter on to the monitor (the monitor's end should be female DVI), and the VGA cable for the XBox 360 (which should male VGA) into the VGA end of the adaptor.