Hi Publius,
Many thanks for your quick response.  My spec is as follows:
CPU :  AMD Phenom II X3 Tri Core 720 Black Edition 2.8GHz (overclocked to 3.3GHz)
Motherboard : Gigabyte GA-MA790XT-UD4P (Socket AM3) PCI Express DDR3
Ram :  Corsair 4GB DDR3 DHX 1600C9DHX Twin3X (2x2GB)
GPU :  Radeon HD5770 x2 (Crossfire)
Hard Drives : 2x Seagate Barracuda 7200.12 500GB SATA-II 16MB Cache - using one drive for Programme files and one for data.
I am running Windows 7 64-bit OS.
I would have thought this is still reasonably high-end, wouldn't you?