j0_77, thanks for the feedback, hopefully it will be useful to a few others.

With regards to video cards, it seems that a few of them do strange things. Here is an extract from a report I get from a WinTv utility:

S3 Vision 868/968 VGA
This hardware is known to use twice the memory it is allocated.
It currently is NOT conflicting with the WinTV hardware.
Manufacturer:: Diamond Multimedia Systems
Description:: Diamond Stealth 64 Series (Diamond GT)

Jon