I'd like to apologise in advance to those long standing members of this forum whom I am likely to offend by my next remark, however....
...._Nothing_ bugs me more in a forum (any forum) than when a dozen people say "No, You Can't Do Something", when YOU CAN!
Windows has included native support for displaying the thumbnail of a bitmap (.bmp) file in 'normal' explorer (ie. not the new Thumbnail view) for as long as I can remember and it is possible to display ANY file's contents as an Explorer thumbnail using an appropriate icon handler - and that includes on the desktop.
Bitmaps are easy since, as I said, they are natively supported in Windows. Open up the Registry Editor (if you're confident enough in your own abilities), find .bmp under HKEY_CLASSES_ROOT and look at the "(Default)" value on the right hand side. It'll probably be something like bmpfile, Paint.Image or OISbmpfile. Whatever it is, scroll down a bit further (on the left) until you find the same text, then expand that folder. You should see a key called "DefaultIcon" and it's "(Default)" value will probably be a file path and name, a comma and a number. Double click this value and replace the text (write it down first) with "%1" (without the quotes). Next time you look at a bitmap file in Explorer or on the desktop (you may need to restart Windows) the icon will be a little thumbnail of the image itself!
JPEG files (or many other image files) are not 'natively' supported by Windows in the same way as bitmaps, so you need to use an icon handler to do the thumbnail creation. What I'm talking about is not one of the many thumbnail generator software applications available to download: An icon handler is a dll that Windows calls to generate thumbnails specifically for display in Explorer (or the desktop). There is one built into Windows 2000/XP, but Adobe Photoshop (including Photoshop SE and Photoshop Elements) has one which seems to work better, and there may be others around.
Activating thumbnails on jpegs is almost the same as for bitmaps, although instead of modifying the DefaultIcon key (leave this as it is), you add a new key called "shellex" (if its not there already), then add another key under that called "IconHandler" and give it the "(Default)" value of "{7376D660-C583-11d0-A3A5-00C04FD706EC}" (without the quotes). If you were using the Photoshop Elements icon handler you would use the value "{C5E6BE25-7388-44f6-8700-88A2D2BD932C}".
More information about Icon Handlers (plus code to make your own!) can be found here:
http://www.codeproject.com/she...xp=0&select=435903
So, there's the correct answer!
Sincere regards,
Mark