This is extremely helpful.
I had used the Steam graphic driver update system, had updated just prior to the DXdiag and assumed it knew what it was doing. The control panel check seemed to confirm that the drivers were up to date. I'm going through the AMD route to re-update anyway.
It seems Supernatural only scores "Maybe" on the 4800 series. Given the minimum spec is 128Mb, and my card is running at 512Mb, there shouldn't have been an issue, but obviously there is!
We've never got as far as running the game- only got as far as CAS.
I won't run it on my daughter's computer- if mine won't run it, it probably will fry hers.
I'll give the testing a run in the next couple of days (life just got busy) with the suggestions you make, and get back to you. What would be a safe maximum for the GPU?
I especially like the suggestion about the new GPU. Whether the wife will...could the "old" GPU be put in the other computer?
Many many thanks!!!