Yes it's the latest from ATI, besides it ran for over a year and then stopped so it's not the version, although I reinstalled jsut in case it was corrupted.
But since my last post I decided a new card was required (different ATI vendor) and unfortunately it does essentially the same thing. So the problem isn't the video card itself, but something indirect - perhaps the power supply or the PCI bus. It's something that's changes after the Windows splash screen.
Had already tried fresh install of Win7. That's how I noticed what the issue was. Ran fine until the first automatic upgrade which installed the ATI driver. Uninstalled just it, alls was well (as well as can be expected anyhow without a video driver).
Also just tried a new power supply - same thing. That pretty well just leaves the motherboard if it's a HW issue. Obviously it could still be software but I have no idea how.