Performance of the Steam version is the issue, which is why I'd dug out the old CDs to try a new installation. That still doesn't run, while the Steam version is slow in the campaign map and lags worse still in battles. As far as I've been able to tell there's no adequate solution to this, but thanks for the responses. It's by no means critical - it seems I could play a scaled down version of Rome on a tablet with better performance. Had been keen to see the game running well with full unit size and high detail, but it looks as though that's going to have to wait a bit yet.