Another update...
After ugrading to Vista and a HDMI (Sapphire 1600 Pro 256mb) graphics card, i've had one or two glitches.
I'm still having problems "applying" any changes to the VGA card when running via HDMI.
I have managed to get 1280x720p @ 50hz to stick, but it still has some slight overscan.
Even with this, the image is much sharper than 1366x768 (my panels native res) via a VGA lead.
I'm not sure why this is, but i'm not complaining!
I added a XBox 360 "HD-DVD" a few days a go, and bought a copy of Cyberlinks PowerDVD Ultra to go with it.
The 360 drive has a built in USB hub, so once connected (and the auto update/driver install performed), you get two extra USB slots.
I've used one with my USB keyboard-track ball, and it works a treat.
I was having some severe problems with Superman Returns (HD-DVD), with crashes and stutters.
However, ATI/Sapphire have just released some new Vista drivers and it seems to have done the trick.
I haven't had any further crashes and playback seems fine.
I still notice the odd stutter, but the disc menus now work and i can navigate the discs.
The Cyberlink software doesn't select the correct video level, meaning blacks are grey and i have had to drop brightness 4 points(in the software player etc) to correct this.
I know its early days, but i assumed running via Vista and HDMI would have sorted this. (i think it is using the older overlay format etc)
Once HD-DVD/Blue Ray (hopefully hybrid) internal drives start shipping for sensible money, i will install one in the case.
But for now, i'm fairly pleased with the results...