This isn't a very urgent problem, but it would be nice to know if there is a solution.
So, I have an HD TV hooked up to my computer for a display, and it does both HDMI and VGA (among others). I have a DVI to HDMI conversion cable from my graphics card to it, as well as a VGA cable.
If I put the TV and graphics card into HDMI mode, then turn off the TV, the graphics card defaults back to VGA and I have to reset the graphics card to HDMI mode again. The only way I've found to have the TV off and still in HDMI mode is to let windows shut the monitor down after going through the screensaver and whatnot.

Is there some setting that controls which display to default to when one or the other is not available?

EDIT: Dunno if it'll help, I have an nVidia 8400 GS. I'll try updating the drivers and see if that helps any.
EDIT2: Didn't fix it.

Hmm, I'm not sure. It's doing the same for mine, but somehow it find a way around it and ends up running fine. I'm with Duh on this one, any help would be appreciated.

I had this sort of problem, my graphics card didn't like the Microsoft WDDM Drivers. You need to use the drivers that came with the graphics card.

1. If your Graphics Card can not support more than 1024x768 then it is not HD and can not support HD.
2. My Xbox is HD (well yh) and it runs of my VGA monitor (only has VGA input) but I can still use it as HD as it is to do with the resolution and not the cable you use. I can't use my computer at the same time as using the Xbox but at least it is HD!

Hope this sort of helps.