Cant See downloaded pictures

Howdy,
when I download any pictures from the internet, using the 'save as' function and put them in either my pictures folder in my users account, or any other folder including a segmented D: or even a removable hard drive - the file copies fine, but when I try and view it I can't.

If I try and download it again - it says it is already there.

If I donwload a pdf, then it works fine, and same with other files. All of my other excisting jpgs etc are stil there and openable???

Any ideas?????

Muchly appreciated.