If you are in Windows Explorer view when initiating the upload you simply need to change to Small or Large Icons and a thumbnail of the image should appear. If no thumbnails are appearing at all, make sure that you have thumbnails enabled under Start -> Search -> Visual Effects
I am using Firefox... The problem is Like here on this board If I go to attachements and then browse and then pictures and a list appears with numbers.. I click on a number in that window but do not know which picture it is because all that is in the preview box is the standard drawing of the mountainand trees.. How do I preview to make sure it is the right picture?