Thanks Raptor I've dowloaded the latest video drivers and this appears to have done the trick.
Many thanks
You should always keep up to date with videocard drivers, but, this issue could have been solved if you had done the following as well:
1. Right click on the Desktop
2. Properties
3. Settings tab
4. Advanced
5. Search for a
tilt tab or something similiar. I only have ATI videocards.