I recently tried this freebie to sort through a couple thousand images and identify/remove the duplicates – it worked like a charm. Its definitely a keeper.

Screen Grab Pro is a free screen capture tool. It features one click grab of any screen for ease of use, timer operation, instant grab of any region, save JPEG, hotkey in any window, and current window selection list. Screen Grab Pro copies a Bitmap to clipboard ready for pasting in your favorite picture editor.

IrfanView is a very fast, small, compact and innovative FREEWARE (for non-commercial use) graphic viewer for Windows 9x/ME/NT/2000/XP/2003/Vista.