Thumbnails not displaying

I have a user who has been using the same Windows 2000 Pro machine for some time. He has not installed or uninstalled any software recently. Yesterday he came to me with the problem that in Windows Explorer when he set the view to Thumbnails all he sees are the large icons. As he spends a lot of time working with pictures this is a real inconvenience.

Any ideas?

Thanks in advance!

mitch@e-mitch.com