Hi Cabbie-uk,
Welcome to Microsoft Answers.
· When was it working fine?
· Was there any changes done to the computer prior to this issue?
Try the below steps.
1. Open Control Panel. (Classic View)
2. Click on the System icon.
3. Click on the advanced system settings link.
4. Under Performance, click on the Settings button.
5. in the Visual Effects tab, Check "Show thumbnails instead of icons."
Change thumbnail size and file details
http://windows.microsoft.com/en-US/windows-vista/Change-thumbnail-size-and-file-details
Diana
Microsoft Answers Support Engineer
Visit our Microsoft Answers Feedback Forum and let us know what you think.